MIR episode 4

47 files changed, 2556 insertions, 804 deletions

diff --git a/crates/base-db/src/change.rs b/crates/base-db/src/change.rs
index fe3792ef6c1..f1973a20714 100644
--- a/crates/base-db/src/change.rs
+++ b/crates/base-db/src/change.rs
@@ -34,7 +34,7 @@ impl fmt::Debug for Change {
 }
 
 impl Change {
-    pub fn new() -> Change {
+    pub fn new() -> Self {
         Change::default()
     }
 
diff --git a/crates/hir-def/src/body/lower.rs b/crates/hir-def/src/body/lower.rs
index 27dfe766d33..d31340fe8f3 100644
--- a/crates/hir-def/src/body/lower.rs
+++ b/crates/hir-def/src/body/lower.rs
@@ -17,7 +17,7 @@ use rustc_hash::FxHashMap;
 use smallvec::SmallVec;
 use syntax::{
     ast::{
-        self, ArrayExprKind, AstChildren, BlockExpr, HasArgList, HasLoopBody, HasName,
+        self, ArrayExprKind, AstChildren, BlockExpr, HasArgList, HasAttrs, HasLoopBody, HasName,
         SlicePatComponents,
     },
     AstNode, AstPtr, SyntaxNodePtr,
@@ -302,16 +302,29 @@ impl ExprCollector<'_> {
                 self.alloc_expr(Expr::For { iterable, pat, body, label }, syntax_ptr)
             }
             ast::Expr::CallExpr(e) => {
-                let callee = self.collect_expr_opt(e.expr());
-                let args = if let Some(arg_list) = e.arg_list() {
-                    arg_list.args().filter_map(|e| self.maybe_collect_expr(e)).collect()
-                } else {
-                    Box::default()
+                let is_rustc_box = {
+                    let attrs = e.attrs();
+                    attrs.filter_map(|x| x.as_simple_atom()).any(|x| x == "rustc_box")
                 };
-                self.alloc_expr(
-                    Expr::Call { callee, args, is_assignee_expr: self.is_lowering_assignee_expr },
-                    syntax_ptr,
-                )
+                if is_rustc_box {
+                    let expr = self.collect_expr_opt(e.arg_list().and_then(|x| x.args().next()));
+                    self.alloc_expr(Expr::Box { expr }, syntax_ptr)
+                } else {
+                    let callee = self.collect_expr_opt(e.expr());
+                    let args = if let Some(arg_list) = e.arg_list() {
+                        arg_list.args().filter_map(|e| self.maybe_collect_expr(e)).collect()
+                    } else {
+                        Box::default()
+                    };
+                    self.alloc_expr(
+                        Expr::Call {
+                            callee,
+                            args,
+                            is_assignee_expr: self.is_lowering_assignee_expr,
+                        },
+                        syntax_ptr,
+                    )
+                }
             }
             ast::Expr::MethodCallExpr(e) => {
                 let receiver = self.collect_expr_opt(e.receiver());
diff --git a/crates/hir-ty/src/builder.rs b/crates/hir-ty/src/builder.rs
index 97924569ccc..2362b08f79a 100644
--- a/crates/hir-ty/src/builder.rs
+++ b/crates/hir-ty/src/builder.rs
@@ -232,6 +232,25 @@ impl TyBuilder<()> {
         TyBuilder::new((), params, parent_subst)
     }
 
+    pub fn subst_for_closure(
+        db: &dyn HirDatabase,
+        parent: DefWithBodyId,
+        sig_ty: Ty,
+    ) -> Substitution {
+        let sig_ty = sig_ty.cast(Interner);
+        let self_subst = iter::once(&sig_ty);
+        let Some(parent) = parent.as_generic_def_id() else {
+            return Substitution::from_iter(Interner, self_subst);
+        };
+        Substitution::from_iter(
+            Interner,
+            self_subst
+                .chain(generics(db.upcast(), parent).placeholder_subst(db).iter(Interner))
+                .cloned()
+                .collect::<Vec<_>>(),
+        )
+    }
+
     pub fn build(self) -> Substitution {
         let ((), subst) = self.build_internal();
         subst
diff --git a/crates/hir-ty/src/chalk_db.rs b/crates/hir-ty/src/chalk_db.rs
index fb7d99711d9..e5be852bc68 100644
--- a/crates/hir-ty/src/chalk_db.rs
+++ b/crates/hir-ty/src/chalk_db.rs
@@ -24,7 +24,7 @@ use crate::{
     method_resolution::{TraitImpls, TyFingerprint, ALL_FLOAT_FPS, ALL_INT_FPS},
     to_assoc_type_id, to_chalk_trait_id,
     traits::ChalkContext,
-    utils::generics,
+    utils::{generics, ClosureSubst},
     wrap_empty_binders, AliasEq, AliasTy, BoundVar, CallableDefId, DebruijnIndex, FnDefId,
     Interner, ProjectionTy, ProjectionTyExt, QuantifiedWhereClause, Substitution, TraitRef,
     TraitRefExt, Ty, TyBuilder, TyExt, TyKind, WhereClause,
@@ -337,7 +337,7 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
         _closure_id: chalk_ir::ClosureId<Interner>,
         substs: &chalk_ir::Substitution<Interner>,
     ) -> chalk_ir::Binders<rust_ir::FnDefInputsAndOutputDatum<Interner>> {
-        let sig_ty = substs.at(Interner, 0).assert_ty_ref(Interner).clone();
+        let sig_ty = ClosureSubst(substs).sig_ty();
         let sig = &sig_ty.callable_sig(self.db).expect("first closure param should be fn ptr");
         let io = rust_ir::FnDefInputsAndOutputDatum {
             argument_types: sig.params().to_vec(),
diff --git a/crates/hir-ty/src/chalk_ext.rs b/crates/hir-ty/src/chalk_ext.rs
index d6a56124856..33c598fe364 100644
--- a/crates/hir-ty/src/chalk_ext.rs
+++ b/crates/hir-ty/src/chalk_ext.rs
@@ -1,20 +1,22 @@
 //! Various extensions traits for Chalk types.
 
-use chalk_ir::{FloatTy, IntTy, Mutability, Scalar, TyVariableKind, UintTy};
+use chalk_ir::{cast::Cast, FloatTy, IntTy, Mutability, Scalar, TyVariableKind, UintTy};
 use hir_def::{
     builtin_type::{BuiltinFloat, BuiltinInt, BuiltinType, BuiltinUint},
     generics::TypeOrConstParamData,
     lang_item::LangItem,
     type_ref::Rawness,
-    FunctionId, GenericDefId, HasModule, ItemContainerId, Lookup, TraitId,
+    DefWithBodyId, FunctionId, GenericDefId, HasModule, ItemContainerId, Lookup, TraitId,
 };
 
 use crate::{
-    db::HirDatabase, from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id,
-    from_placeholder_idx, to_chalk_trait_id, utils::generics, AdtId, AliasEq, AliasTy, Binders,
-    CallableDefId, CallableSig, ClosureId, DynTy, FnPointer, ImplTraitId, Interner, Lifetime,
-    ProjectionTy, QuantifiedWhereClause, Substitution, TraitRef, Ty, TyBuilder, TyKind, TypeFlags,
-    WhereClause,
+    db::HirDatabase,
+    from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id, from_placeholder_idx,
+    to_chalk_trait_id,
+    utils::{generics, ClosureSubst},
+    AdtId, AliasEq, AliasTy, Binders, CallableDefId, CallableSig, Canonical, CanonicalVarKinds,
+    ClosureId, DynTy, FnPointer, ImplTraitId, InEnvironment, Interner, Lifetime, ProjectionTy,
+    QuantifiedWhereClause, Substitution, TraitRef, Ty, TyBuilder, TyKind, TypeFlags, WhereClause,
 };
 
 pub trait TyExt {
@@ -46,6 +48,7 @@ pub trait TyExt {
 
     fn impl_trait_bounds(&self, db: &dyn HirDatabase) -> Option<Vec<QuantifiedWhereClause>>;
     fn associated_type_parent_trait(&self, db: &dyn HirDatabase) -> Option<TraitId>;
+    fn is_copy(self, db: &dyn HirDatabase, owner: DefWithBodyId) -> bool;
 
     /// FIXME: Get rid of this, it's not a good abstraction
     fn equals_ctor(&self, other: &Ty) -> bool;
@@ -185,10 +188,7 @@ impl TyExt for Ty {
                 let sig = db.callable_item_signature(callable_def);
                 Some(sig.substitute(Interner, parameters))
             }
-            TyKind::Closure(.., substs) => {
-                let sig_param = substs.at(Interner, 0).assert_ty_ref(Interner);
-                sig_param.callable_sig(db)
-            }
+            TyKind::Closure(.., substs) => ClosureSubst(substs).sig_ty().callable_sig(db),
             _ => None,
         }
     }
@@ -327,6 +327,20 @@ impl TyExt for Ty {
         }
     }
 
+    fn is_copy(self, db: &dyn HirDatabase, owner: DefWithBodyId) -> bool {
+        let crate_id = owner.module(db.upcast()).krate();
+        let Some(copy_trait) = db.lang_item(crate_id, LangItem::Copy).and_then(|x| x.as_trait()) else {
+            return false;
+        };
+        let trait_ref = TyBuilder::trait_ref(db, copy_trait).push(self).build();
+        let env = db.trait_environment_for_body(owner);
+        let goal = Canonical {
+            value: InEnvironment::new(&env.env, trait_ref.cast(Interner)),
+            binders: CanonicalVarKinds::empty(Interner),
+        };
+        db.trait_solve(crate_id, None, goal).is_some()
+    }
+
     fn equals_ctor(&self, other: &Ty) -> bool {
         match (self.kind(Interner), other.kind(Interner)) {
             (TyKind::Adt(adt, ..), TyKind::Adt(adt2, ..)) => adt == adt2,
diff --git a/crates/hir-ty/src/consteval.rs b/crates/hir-ty/src/consteval.rs
index 78033b4e89b..80b72768b3c 100644
--- a/crates/hir-ty/src/consteval.rs
+++ b/crates/hir-ty/src/consteval.rs
@@ -7,7 +7,7 @@ use hir_def::{
     path::Path,
     resolver::{Resolver, ValueNs},
     type_ref::ConstRef,
-    ConstId, EnumVariantId,
+    DefWithBodyId, EnumVariantId,
 };
 use la_arena::{Idx, RawIdx};
 use stdx::never;
@@ -57,7 +57,7 @@ pub enum ConstEvalError {
 impl From<MirLowerError> for ConstEvalError {
     fn from(value: MirLowerError) -> Self {
         match value {
-            MirLowerError::ConstEvalError(e) => *e,
+            MirLowerError::ConstEvalError(_, e) => *e,
             _ => ConstEvalError::MirLowerError(value),
         }
     }
@@ -168,7 +168,7 @@ pub fn try_const_usize(c: &Const) -> Option<u128> {
 pub(crate) fn const_eval_recover(
     _: &dyn HirDatabase,
     _: &[String],
-    _: &ConstId,
+    _: &DefWithBodyId,
     _: &Substitution,
 ) -> Result<Const, ConstEvalError> {
     Err(ConstEvalError::MirLowerError(MirLowerError::Loop))
@@ -184,10 +184,9 @@ pub(crate) fn const_eval_discriminant_recover(
 
 pub(crate) fn const_eval_query(
     db: &dyn HirDatabase,
-    const_id: ConstId,
+    def: DefWithBodyId,
     subst: Substitution,
 ) -> Result<Const, ConstEvalError> {
-    let def = const_id.into();
     let body = db.mir_body(def)?;
     let c = interpret_mir(db, &body, subst, false)?;
     Ok(c)
diff --git a/crates/hir-ty/src/consteval/tests.rs b/crates/hir-ty/src/consteval/tests.rs
index d987f41c706..e95e1755363 100644
--- a/crates/hir-ty/src/consteval/tests.rs
+++ b/crates/hir-ty/src/consteval/tests.rs
@@ -1,4 +1,4 @@
-use base_db::fixture::WithFixture;
+use base_db::{fixture::WithFixture, FileId};
 use chalk_ir::Substitution;
 use hir_def::db::DefDatabase;
 
@@ -16,7 +16,7 @@ mod intrinsics;
 
 fn simplify(e: ConstEvalError) -> ConstEvalError {
     match e {
-        ConstEvalError::MirEvalError(MirEvalError::InFunction(_, e)) => {
+        ConstEvalError::MirEvalError(MirEvalError::InFunction(_, e, _, _)) => {
             simplify(ConstEvalError::MirEvalError(*e))
         }
         _ => e,
@@ -24,13 +24,30 @@ fn simplify(e: ConstEvalError) -> ConstEvalError {
 }
 
 #[track_caller]
-fn check_fail(ra_fixture: &str, error: ConstEvalError) {
-    assert_eq!(eval_goal(ra_fixture).map_err(simplify), Err(error));
+fn check_fail(ra_fixture: &str, error: impl FnOnce(ConstEvalError) -> bool) {
+    let (db, file_id) = TestDB::with_single_file(ra_fixture);
+    match eval_goal(&db, file_id).map_err(simplify) {
+        Ok(_) => panic!("Expected fail, but it succeeded"),
+        Err(e) => assert!(error(e)),
+    }
 }
 
 #[track_caller]
 fn check_number(ra_fixture: &str, answer: i128) {
-    let r = eval_goal(ra_fixture).unwrap();
+    let (db, file_id) = TestDB::with_single_file(ra_fixture);
+    let r = match eval_goal(&db, file_id) {
+        Ok(t) => t,
+        Err(e) => {
+            let mut err = String::new();
+            let span_formatter = |file, range| format!("{:?} {:?}", file, range);
+            match e {
+                ConstEvalError::MirLowerError(e) => e.pretty_print(&mut err, &db, span_formatter),
+                ConstEvalError::MirEvalError(e) => e.pretty_print(&mut err, &db, span_formatter),
+            }
+            .unwrap();
+            panic!("Error in evaluating goal: {}", err);
+        }
+    };
     match &r.data(Interner).value {
         chalk_ir::ConstValue::Concrete(c) => match &c.interned {
             ConstScalar::Bytes(b, _) => {
@@ -47,10 +64,9 @@ fn check_number(ra_fixture: &str, answer: i128) {
     }
 }
 
-fn eval_goal(ra_fixture: &str) -> Result<Const, ConstEvalError> {
-    let (db, file_id) = TestDB::with_single_file(ra_fixture);
+fn eval_goal(db: &TestDB, file_id: FileId) -> Result<Const, ConstEvalError> {
     let module_id = db.module_for_file(file_id);
-    let def_map = module_id.def_map(&db);
+    let def_map = module_id.def_map(db);
     let scope = &def_map[module_id.local_id].scope;
     let const_id = scope
         .declarations()
@@ -65,7 +81,7 @@ fn eval_goal(ra_fixture: &str) -> Result<Const, ConstEvalError> {
             _ => None,
         })
         .unwrap();
-    db.const_eval(const_id, Substitution::empty(Interner))
+    db.const_eval(const_id.into(), Substitution::empty(Interner))
 }
 
 #[test]
@@ -304,6 +320,81 @@ fn overloaded_index() {
 }
 
 #[test]
+fn overloaded_binop() {
+    check_number(
+        r#"
+    //- minicore: add
+    enum Color {
+        Red,
+        Green,
+        Yellow,
+    }
+
+    use Color::*;
+
+    impl core::ops::Add for Color {
+        type Output = Color;
+        fn add(self, rhs: Color) -> Self::Output {
+            Yellow
+        }
+    }
+
+    impl core::ops::AddAssign for Color {
+        fn add_assign(&mut self, rhs: Color) {
+            *self = Red;
+        }
+    }
+
+    const GOAL: bool = {
+        let x = Red + Green;
+        let mut y = Green;
+        y += x;
+        x == Yellow && y == Red && Red + Green == Yellow && Red + Red == Yellow && Yellow + Green == Yellow
+    };
+    "#,
+        1,
+    );
+    check_number(
+        r#"
+    //- minicore: add
+    impl core::ops::Add for usize {
+        type Output = usize;
+        fn add(self, rhs: usize) -> Self::Output {
+            self + rhs
+        }
+    }
+
+    impl core::ops::AddAssign for usize {
+        fn add_assign(&mut self, rhs: usize) {
+            *self += rhs;
+        }
+    }
+
+    #[lang = "shl"]
+    pub trait Shl<Rhs = Self> {
+        type Output;
+
+        fn shl(self, rhs: Rhs) -> Self::Output;
+    }
+
+    impl Shl<u8> for usize {
+        type Output = usize;
+
+        fn shl(self, rhs: u8) -> Self::Output {
+            self << rhs
+        }
+    }
+
+    const GOAL: usize = {
+        let mut x = 10;
+        x += 20;
+        2 + 2 + (x << 1u8)
+    };"#,
+        64,
+    );
+}
+
+#[test]
 fn function_call() {
     check_number(
         r#"
@@ -428,6 +519,16 @@ fn generic_fn() {
     );
     check_number(
         r#"
+        const fn y<T>(b: T) -> (T, ) {
+            let alloc = b;
+            (alloc, )
+        }
+        const GOAL: u8 = y(2).0;
+        "#,
+        2,
+    );
+    check_number(
+        r#"
     //- minicore: coerce_unsized, index, slice
     fn bar<A, B>(a: A, b: B) -> B {
         b
@@ -590,6 +691,30 @@ fn loops() {
         "#,
         8,
     );
+    check_number(
+        r#"
+    //- minicore: add
+    const GOAL: u8 = {
+        let mut x = 0;
+        'a: loop {
+            'b: loop {
+                'c: while x < 20 {
+                    'd: while x < 5 {
+                        'e: loop {
+                            x += 1;
+                            continue 'c;
+                        };
+                    };
+                    x += 1;
+                };
+                break 'a;
+            };
+        }
+        x
+    };
+        "#,
+        20,
+    );
 }
 
 #[test]
@@ -790,10 +915,12 @@ fn path_pattern_matching() {
 
     use Season::*;
 
+    const MY_SEASON: Season = Summer;
+
     const fn f(x: Season) -> i32 {
         match x {
             Spring => 1,
-            Summer => 2,
+            MY_SEASON => 2,
             Fall => 3,
             Winter => 4,
         }
@@ -944,19 +1071,10 @@ fn function_param_patterns() {
 fn match_guards() {
     check_number(
         r#"
-    //- minicore: option, eq
-    impl<T: PartialEq> PartialEq for Option<T> {
-        fn eq(&self, other: &Rhs) -> bool {
-            match (self, other) {
-                (Some(x), Some(y)) => x == y,
-                (None, None) => true,
-                _ => false,
-            }
-        }
-    }
+    //- minicore: option
     fn f(x: Option<i32>) -> i32 {
         match x {
-            y if y == Some(42) => 42000,
+            y if let Some(42) = y => 42000,
             Some(y) => y,
             None => 10
         }
@@ -968,6 +1086,59 @@ fn match_guards() {
 }
 
 #[test]
+fn result_layout_niche_optimization() {
+    check_number(
+        r#"
+    //- minicore: option, result
+    const GOAL: i32 = match Some(2).ok_or(Some(2)) {
+        Ok(x) => x,
+        Err(_) => 1000,
+    };
+        "#,
+        2,
+    );
+    check_number(
+        r#"
+    //- minicore: result
+    pub enum AlignmentEnum64 {
+        _Align1Shl0 = 1 << 0,
+        _Align1Shl1 = 1 << 1,
+        _Align1Shl2 = 1 << 2,
+        _Align1Shl3 = 1 << 3,
+        _Align1Shl4 = 1 << 4,
+        _Align1Shl5 = 1 << 5,
+    }
+    const GOAL: Result<AlignmentEnum64, ()> = {
+        let align = Err(());
+        align
+    };
+    "#,
+        0, // It is 0 since result is niche encoded and 1 is valid for `AlignmentEnum64`
+    );
+    check_number(
+        r#"
+    //- minicore: result
+    pub enum AlignmentEnum64 {
+        _Align1Shl0 = 1 << 0,
+        _Align1Shl1 = 1 << 1,
+        _Align1Shl2 = 1 << 2,
+        _Align1Shl3 = 1 << 3,
+        _Align1Shl4 = 1 << 4,
+        _Align1Shl5 = 1 << 5,
+    }
+    const GOAL: i32 = {
+        let align = Ok::<_, ()>(AlignmentEnum64::_Align1Shl0);
+        match align {
+            Ok(_) => 2,
+            Err(_) => 1,
+        }
+    };
+    "#,
+        2,
+    );
+}
+
+#[test]
 fn options() {
     check_number(
         r#"
@@ -1147,6 +1318,16 @@ fn closures() {
     check_number(
         r#"
     //- minicore: fn, copy
+    const GOAL: i32 = {
+        let c: fn(i32) -> i32 = |x| 2 * x;
+        c(2) + c(10)
+    };
+        "#,
+        24,
+    );
+    check_number(
+        r#"
+    //- minicore: fn, copy
     struct X(i32);
     impl X {
         fn mult(&mut self, n: i32) {
@@ -1181,6 +1362,36 @@ fn closures() {
 }
 
 #[test]
+fn closure_and_impl_fn() {
+    check_number(
+        r#"
+    //- minicore: fn, copy
+    fn closure_wrapper<F: FnOnce() -> i32>(c: F) -> impl FnOnce() -> F {
+        || c
+    }
+
+    const GOAL: i32 = {
+        let y = 5;
+        let c = closure_wrapper(|| y);
+        c()()
+    };
+        "#,
+        5,
+    );
+    check_number(
+        r#"
+    //- minicore: fn, copy
+    fn f<T, F: Fn() -> T>(t: F) -> impl Fn() -> T {
+        move || t()
+    }
+
+    const GOAL: i32 = f(|| 2)();
+        "#,
+        2,
+    );
+}
+
+#[test]
 fn or_pattern() {
     check_number(
         r#"
@@ -1219,6 +1430,23 @@ fn or_pattern() {
 }
 
 #[test]
+fn function_pointer_in_constants() {
+    check_number(
+        r#"
+    struct Foo {
+        f: fn(u8) -> u8,
+    }
+    const FOO: Foo = Foo { f: add2 };
+    fn add2(x: u8) -> u8 {
+        x + 2
+    }
+    const GOAL: u8 = (FOO.f)(3);
+        "#,
+        5,
+    );
+}
+
+#[test]
 fn function_pointer() {
     check_number(
         r#"
@@ -1433,6 +1661,51 @@ fn dyn_trait() {
 }
 
 #[test]
+fn boxes() {
+    check_number(
+        r#"
+//- minicore: coerce_unsized, deref_mut, slice
+use core::ops::{Deref, DerefMut};
+use core::{marker::Unsize, ops::CoerceUnsized};
+
+#[lang = "owned_box"]
+pub struct Box<T: ?Sized> {
+    inner: *mut T,
+}
+impl<T> Box<T> {
+    fn new(t: T) -> Self {
+        #[rustc_box]
+        Box::new(t)
+    }
+}
+
+impl<T: ?Sized> Deref for Box<T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        &**self
+    }
+}
+
+impl<T: ?Sized> DerefMut for Box<T> {
+    fn deref_mut(&mut self) -> &mut T {
+        &mut **self
+    }
+}
+
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Box<U>> for Box<T> {}
+
+const GOAL: usize = {
+    let x = Box::new(5);
+    let y: Box<[i32]> = Box::new([1, 2, 3]);
+    *x + y.len()
+};
+"#,
+        8,
+    );
+}
+
+#[test]
 fn array_and_index() {
     check_number(
         r#"
@@ -1505,6 +1778,37 @@ fn consts() {
 }
 
 #[test]
+fn statics() {
+    check_number(
+        r#"
+    //- minicore: cell
+    use core::cell::Cell;
+    fn f() -> i32 {
+        static S: Cell<i32> = Cell::new(10);
+        S.set(S.get() + 1);
+        S.get()
+    }
+    const GOAL: i32 = f() + f() + f();
+    "#,
+        36,
+    );
+}
+
+#[test]
+fn extern_weak_statics() {
+    check_number(
+        r#"
+    extern "C" {
+        #[linkage = "extern_weak"]
+        static __dso_handle: *mut u8;
+    }
+    const GOAL: usize = __dso_handle as usize;
+    "#,
+        0,
+    );
+}
+
+#[test]
 fn enums() {
     check_number(
         r#"
@@ -1531,13 +1835,13 @@ fn enums() {
     "#,
         0,
     );
-    let r = eval_goal(
+    let (db, file_id) = TestDB::with_single_file(
         r#"
         enum E { A = 1, B }
         const GOAL: E = E::A;
         "#,
-    )
-    .unwrap();
+    );
+    let r = eval_goal(&db, file_id).unwrap();
     assert_eq!(try_const_usize(&r), Some(1));
 }
 
@@ -1550,7 +1854,7 @@ fn const_loop() {
     const F2: i32 = 2 * F1;
     const GOAL: i32 = F3;
     "#,
-        ConstEvalError::MirLowerError(MirLowerError::Loop),
+        |e| e == ConstEvalError::MirLowerError(MirLowerError::Loop),
     );
 }
 
@@ -1609,8 +1913,7 @@ fn const_generic_subst_assoc_const_impl() {
 
 #[test]
 fn const_trait_assoc() {
-    // FIXME: this should evaluate to 0
-    check_fail(
+    check_number(
         r#"
     struct U0;
     trait ToConst {
@@ -1619,9 +1922,35 @@ fn const_trait_assoc() {
     impl ToConst for U0 {
         const VAL: usize = 0;
     }
-    const GOAL: usize = U0::VAL;
+    impl ToConst for i32 {
+        const VAL: usize = 32;
+    }
+    const GOAL: usize = U0::VAL + i32::VAL;
     "#,
-        ConstEvalError::MirLowerError(MirLowerError::IncompleteExpr),
+        32,
+    );
+    check_number(
+        r#"
+    struct S<T>(*mut T);
+
+    trait MySized: Sized {
+        const SIZE: S<Self> = S(1 as *mut Self);
+    }
+
+    impl MySized for i32 {
+        const SIZE: S<i32> = S(10 as *mut i32);
+    }
+
+    impl MySized for i64 {
+    }
+
+    const fn f<T: MySized>() -> usize {
+        T::SIZE.0 as usize
+    }
+
+    const GOAL: usize = f::<i32>() + f::<i64>() * 2;
+    "#,
+        12,
     );
 }
 
@@ -1631,7 +1960,7 @@ fn exec_limits() {
         r#"
     const GOAL: usize = loop {};
     "#,
-        ConstEvalError::MirEvalError(MirEvalError::ExecutionLimitExceeded),
+        |e| e == ConstEvalError::MirEvalError(MirEvalError::ExecutionLimitExceeded),
     );
     check_fail(
         r#"
@@ -1640,7 +1969,7 @@ fn exec_limits() {
     }
     const GOAL: i32 = f(0);
     "#,
-        ConstEvalError::MirEvalError(MirEvalError::StackOverflow),
+        |e| e == ConstEvalError::MirEvalError(MirEvalError::StackOverflow),
     );
     // Reasonable code should still work
     check_number(
@@ -1665,7 +1994,7 @@ fn exec_limits() {
 
 #[test]
 fn type_error() {
-    let e = eval_goal(
+    check_fail(
         r#"
     const GOAL: u8 = {
         let x: u16 = 2;
@@ -1673,6 +2002,6 @@ fn type_error() {
         y.0
     };
     "#,
+        |e| matches!(e, ConstEvalError::MirLowerError(MirLowerError::TypeMismatch(_))),
     );
-    assert!(matches!(e, Err(ConstEvalError::MirLowerError(MirLowerError::TypeMismatch(_)))));
 }
diff --git a/crates/hir-ty/src/consteval/tests/intrinsics.rs b/crates/hir-ty/src/consteval/tests/intrinsics.rs
index 5c47e1f00a4..40e68823acd 100644
--- a/crates/hir-ty/src/consteval/tests/intrinsics.rs
+++ b/crates/hir-ty/src/consteval/tests/intrinsics.rs
@@ -68,6 +68,135 @@ fn wrapping_add() {
 }
 
 #[test]
+fn allocator() {
+    check_number(
+        r#"
+        extern "Rust" {
+            #[rustc_allocator]
+            fn __rust_alloc(size: usize, align: usize) -> *mut u8;
+            #[rustc_deallocator]
+            fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
+            #[rustc_reallocator]
+            fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;
+            #[rustc_allocator_zeroed]
+            fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
+        }
+
+        const GOAL: u8 = unsafe {
+            let ptr = __rust_alloc(4, 1);
+            let ptr2 = ((ptr as usize) + 1) as *mut u8;
+            *ptr = 23;
+            *ptr2 = 32;
+            let ptr = __rust_realloc(ptr, 4, 1, 8);
+            let ptr2 = ((ptr as usize) + 1) as *mut u8;
+            *ptr + *ptr2
+        };
+        "#,
+        55,
+    );
+}
+
+#[test]
+fn overflowing_add() {
+    check_number(
+        r#"
+        extern "rust-intrinsic" {
+            pub fn add_with_overflow<T>(x: T, y: T) -> (T, bool);
+        }
+
+        const GOAL: u8 = add_with_overflow(1, 2).0;
+        "#,
+        3,
+    );
+    check_number(
+        r#"
+        extern "rust-intrinsic" {
+            pub fn add_with_overflow<T>(x: T, y: T) -> (T, bool);
+        }
+
+        const GOAL: u8 = add_with_overflow(1, 2).1 as u8;
+        "#,
+        0,
+    );
+}
+
+#[test]
+fn needs_drop() {
+    check_number(
+        r#"
+        //- minicore: copy, sized
+        extern "rust-intrinsic" {
+            pub fn needs_drop<T: ?Sized>() -> bool;
+        }
+        struct X;
+        const GOAL: bool = !needs_drop::<i32>() && needs_drop::<X>();
+        "#,
+        1,
+    );
+}
+
+#[test]
+fn likely() {
+    check_number(
+        r#"
+        extern "rust-intrinsic" {
+            pub fn likely(b: bool) -> bool;
+            pub fn unlikely(b: bool) -> bool;
+        }
+
+        const GOAL: bool = likely(true) && unlikely(true) && !likely(false) && !unlikely(false);
+        "#,
+        1,
+    );
+}
+
+#[test]
+fn atomic() {
+    check_number(
+        r#"
+        //- minicore: copy
+        extern "rust-intrinsic" {
+            pub fn atomic_load_seqcst<T: Copy>(src: *const T) -> T;
+            pub fn atomic_xchg_acquire<T: Copy>(dst: *mut T, src: T) -> T;
+            pub fn atomic_cxchg_release_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
+            pub fn atomic_cxchgweak_acquire_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
+            pub fn atomic_store_release<T: Copy>(dst: *mut T, val: T);
+            pub fn atomic_xadd_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
+            pub fn atomic_xsub_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
+            pub fn atomic_and_acquire<T: Copy>(dst: *mut T, src: T) -> T;
+            pub fn atomic_nand_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
+            pub fn atomic_or_release<T: Copy>(dst: *mut T, src: T) -> T;
+            pub fn atomic_xor_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
+        }
+
+        fn should_not_reach() {
+            _ // fails the test if executed
+        }
+
+        const GOAL: i32 = {
+            let mut x = 5;
+            atomic_store_release(&mut x, 10);
+            let mut y = atomic_xchg_acquire(&mut x, 100);
+            atomic_xadd_acqrel(&mut y, 20);
+            if (30, true) != atomic_cxchg_release_seqcst(&mut y, 30, 40) {
+                should_not_reach();
+            }
+            if (40, false) != atomic_cxchg_release_seqcst(&mut y, 30, 50) {
+                should_not_reach();
+            }
+            if (40, true) != atomic_cxchgweak_acquire_acquire(&mut y, 40, 30) {
+                should_not_reach();
+            }
+            let mut z = atomic_xsub_seqcst(&mut x, -200);
+            atomic_xor_seqcst(&mut x, 1024);
+            atomic_load_seqcst(&x) + z * 3 + atomic_load_seqcst(&y) * 2
+        };
+        "#,
+        660 + 1024,
+    );
+}
+
+#[test]
 fn offset() {
     check_number(
         r#"
diff --git a/crates/hir-ty/src/db.rs b/crates/hir-ty/src/db.rs
index c415689399f..963b3b72abb 100644
--- a/crates/hir-ty/src/db.rs
+++ b/crates/hir-ty/src/db.rs
@@ -5,7 +5,7 @@ use std::sync::Arc;
 
 use base_db::{impl_intern_key, salsa, CrateId, Upcast};
 use hir_def::{
-    db::DefDatabase, hir::ExprId, layout::TargetDataLayout, AdtId, BlockId, ConstId, ConstParamId,
+    db::DefDatabase, hir::ExprId, layout::TargetDataLayout, AdtId, BlockId, ConstParamId,
     DefWithBodyId, EnumVariantId, FunctionId, GenericDefId, ImplId, LifetimeParamId, LocalFieldId,
     TypeOrConstParamId, VariantId,
 };
@@ -59,7 +59,7 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
 
     #[salsa::invoke(crate::consteval::const_eval_query)]
     #[salsa::cycle(crate::consteval::const_eval_recover)]
-    fn const_eval(&self, def: ConstId, subst: Substitution) -> Result<Const, ConstEvalError>;
+    fn const_eval(&self, def: DefWithBodyId, subst: Substitution) -> Result<Const, ConstEvalError>;
 
     #[salsa::invoke(crate::consteval::const_eval_discriminant_variant)]
     #[salsa::cycle(crate::consteval::const_eval_discriminant_recover)]
diff --git a/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs b/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs
index 7460f43387f..a0f6b9368ee 100644
--- a/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs
+++ b/crates/hir-ty/src/diagnostics/match_check/deconstruct_pat.rs
@@ -772,7 +772,7 @@ impl<'p> Fields<'p> {
 
         (0..fields_len).map(|idx| LocalFieldId::from_raw(idx.into())).filter_map(move |fid| {
             let ty = field_ty[fid].clone().substitute(Interner, substs);
-            let ty = normalize(cx.db, cx.body, ty);
+            let ty = normalize(cx.db, cx.db.trait_environment_for_body(cx.body), ty);
             let is_visible = matches!(adt, hir_def::AdtId::EnumId(..))
                 || visibility[fid].is_visible_from(cx.db.upcast(), cx.module);
             let is_uninhabited = cx.is_uninhabited(&ty);
diff --git a/crates/hir-ty/src/display.rs b/crates/hir-ty/src/display.rs
index d445abae923..3cfe78141d4 100644
--- a/crates/hir-ty/src/display.rs
+++ b/crates/hir-ty/src/display.rs
@@ -32,7 +32,7 @@ use crate::{
     mapping::from_chalk,
     mir::pad16,
     primitive, to_assoc_type_id,
-    utils::{self, generics},
+    utils::{self, generics, ClosureSubst},
     AdtId, AliasEq, AliasTy, Binders, CallableDefId, CallableSig, Const, ConstScalar, ConstValue,
     DomainGoal, GenericArg, ImplTraitId, Interner, Lifetime, LifetimeData, LifetimeOutlives,
     MemoryMap, Mutability, OpaqueTy, ProjectionTy, ProjectionTyExt, QuantifiedWhereClause, Scalar,
@@ -419,6 +419,16 @@ impl HirDisplay for Const {
             }
             ConstValue::Concrete(c) => match &c.interned {
                 ConstScalar::Bytes(b, m) => render_const_scalar(f, &b, m, &data.ty),
+                ConstScalar::UnevaluatedConst(c, parameters) => {
+                    let const_data = f.db.const_data(*c);
+                    write!(
+                        f,
+                        "{}",
+                        const_data.name.as_ref().and_then(|x| x.as_str()).unwrap_or("_")
+                    )?;
+                    hir_fmt_generics(f, parameters, Some((*c).into()))?;
+                    Ok(())
+                }
                 ConstScalar::Unknown => f.write_char('_'),
             },
         }
@@ -485,7 +495,7 @@ fn render_const_scalar(
         chalk_ir::TyKind::Ref(_, _, t) => match t.kind(Interner) {
             chalk_ir::TyKind::Str => {
                 let addr = usize::from_le_bytes(b[0..b.len() / 2].try_into().unwrap());
-                let bytes = memory_map.0.get(&addr).map(|x| &**x).unwrap_or(&[]);
+                let bytes = memory_map.memory.get(&addr).map(|x| &**x).unwrap_or(&[]);
                 let s = std::str::from_utf8(bytes).unwrap_or("<utf8-error>");
                 write!(f, "{s:?}")
             }
@@ -574,6 +584,11 @@ fn render_const_scalar(
             hir_def::AdtId::EnumId(_) => f.write_str("<enum-not-supported>"),
         },
         chalk_ir::TyKind::FnDef(..) => ty.hir_fmt(f),
+        chalk_ir::TyKind::Raw(_, _) => {
+            let x = u128::from_le_bytes(pad16(b, false));
+            write!(f, "{:#X} as ", x)?;
+            ty.hir_fmt(f)
+        }
         _ => f.write_str("<not-supported>"),
     }
 }
@@ -794,82 +809,9 @@ impl HirDisplay for Ty {
                 }
                 f.end_location_link();
 
-                if parameters.len(Interner) > 0 {
-                    let parameters_to_write = if f.display_target.is_source_code()
-                        || f.omit_verbose_types()
-                    {
-                        match self
-                            .as_generic_def(db)
-                            .map(|generic_def_id| db.generic_defaults(generic_def_id))
-                            .filter(|defaults| !defaults.is_empty())
-                        {
-                            None => parameters.as_slice(Interner),
-                            Some(default_parameters) => {
-                                fn should_show(
-                                    parameter: &GenericArg,
-                                    default_parameters: &[Binders<GenericArg>],
-                                    i: usize,
-                                    parameters: &Substitution,
-                                ) -> bool {
-                                    if parameter.ty(Interner).map(|x| x.kind(Interner))
-                                        == Some(&TyKind::Error)
-                                    {
-                                        return true;
-                                    }
-                                    if let Some(ConstValue::Concrete(c)) = parameter
-                                        .constant(Interner)
-                                        .map(|x| &x.data(Interner).value)
-                                    {
-                                        if c.interned == ConstScalar::Unknown {
-                                            return true;
-                                        }
-                                    }
-                                    let default_parameter = match default_parameters.get(i) {
-                                        Some(x) => x,
-                                        None => return true,
-                                    };
-                                    let actual_default =
-                                        default_parameter.clone().substitute(Interner, &parameters);
-                                    parameter != &actual_default
-                                }
-                                let mut default_from = 0;
-                                for (i, parameter) in parameters.iter(Interner).enumerate() {
-                                    if should_show(parameter, &default_parameters, i, parameters) {
-                                        default_from = i + 1;
-                                    }
-                                }
-                                &parameters.as_slice(Interner)[0..default_from]
-                            }
-                        }
-                    } else {
-                        parameters.as_slice(Interner)
-                    };
-                    if !parameters_to_write.is_empty() {
-                        write!(f, "<")?;
-
-                        if f.display_target.is_source_code() {
-                            let mut first = true;
-                            for generic_arg in parameters_to_write {
-                                if !first {
-                                    write!(f, ", ")?;
-                                }
-                                first = false;
-
-                                if generic_arg.ty(Interner).map(|ty| ty.kind(Interner))
-                                    == Some(&TyKind::Error)
-                                {
-                                    write!(f, "_")?;
-                                } else {
-                                    generic_arg.hir_fmt(f)?;
-                                }
-                            }
-                        } else {
-                            f.write_joined(parameters_to_write, ", ")?;
-                        }
+                let generic_def = self.as_generic_def(db);
 
-                        write!(f, ">")?;
-                    }
-                }
+                hir_fmt_generics(f, parameters, generic_def)?;
             }
             TyKind::AssociatedType(assoc_type_id, parameters) => {
                 let type_alias = from_assoc_type_id(*assoc_type_id);
@@ -983,7 +925,7 @@ impl HirDisplay for Ty {
                     }
                     _ => (),
                 }
-                let sig = substs.at(Interner, 0).assert_ty_ref(Interner).callable_sig(db);
+                let sig = ClosureSubst(substs).sig_ty().callable_sig(db);
                 if let Some(sig) = sig {
                     let (def, _) = db.lookup_intern_closure((*id).into());
                     let infer = db.infer(def);
@@ -1141,6 +1083,85 @@ impl HirDisplay for Ty {
     }
 }
 
+fn hir_fmt_generics(
+    f: &mut HirFormatter<'_>,
+    parameters: &Substitution,
+    generic_def: Option<hir_def::GenericDefId>,
+) -> Result<(), HirDisplayError> {
+    let db = f.db;
+    if parameters.len(Interner) > 0 {
+        let parameters_to_write = if f.display_target.is_source_code() || f.omit_verbose_types() {
+            match generic_def
+                .map(|generic_def_id| db.generic_defaults(generic_def_id))
+                .filter(|defaults| !defaults.is_empty())
+            {
+                None => parameters.as_slice(Interner),
+                Some(default_parameters) => {
+                    fn should_show(
+                        parameter: &GenericArg,
+                        default_parameters: &[Binders<GenericArg>],
+                        i: usize,
+                        parameters: &Substitution,
+                    ) -> bool {
+                        if parameter.ty(Interner).map(|x| x.kind(Interner)) == Some(&TyKind::Error)
+                        {
+                            return true;
+                        }
+                        if let Some(ConstValue::Concrete(c)) =
+                            parameter.constant(Interner).map(|x| &x.data(Interner).value)
+                        {
+                            if c.interned == ConstScalar::Unknown {
+                                return true;
+                            }
+                        }
+                        let default_parameter = match default_parameters.get(i) {
+                            Some(x) => x,
+                            None => return true,
+                        };
+                        let actual_default =
+                            default_parameter.clone().substitute(Interner, &parameters);
+                        parameter != &actual_default
+                    }
+                    let mut default_from = 0;
+                    for (i, parameter) in parameters.iter(Interner).enumerate() {
+                        if should_show(parameter, &default_parameters, i, parameters) {
+                            default_from = i + 1;
+                        }
+                    }
+                    &parameters.as_slice(Interner)[0..default_from]
+                }
+            }
+        } else {
+            parameters.as_slice(Interner)
+        };
+        if !parameters_to_write.is_empty() {
+            write!(f, "<")?;
+
+            if f.display_target.is_source_code() {
+                let mut first = true;
+                for generic_arg in parameters_to_write {
+                    if !first {
+                        write!(f, ", ")?;
+                    }
+                    first = false;
+
+                    if generic_arg.ty(Interner).map(|ty| ty.kind(Interner)) == Some(&TyKind::Error)
+                    {
+                        write!(f, "_")?;
+                    } else {
+                        generic_arg.hir_fmt(f)?;
+                    }
+                }
+            } else {
+                f.write_joined(parameters_to_write, ", ")?;
+            }
+
+            write!(f, ">")?;
+        }
+    }
+    Ok(())
+}
+
 impl HirDisplay for CallableSig {
     fn hir_fmt(&self, f: &mut HirFormatter<'_>) -> Result<(), HirDisplayError> {
         write!(f, "fn(")?;
diff --git a/crates/hir-ty/src/infer.rs b/crates/hir-ty/src/infer.rs
index 64e31583095..ba0b6d254b7 100644
--- a/crates/hir-ty/src/infer.rs
+++ b/crates/hir-ty/src/infer.rs
@@ -44,7 +44,7 @@ use crate::{
     db::HirDatabase, fold_tys, infer::coerce::CoerceMany, lower::ImplTraitLoweringMode,
     static_lifetime, to_assoc_type_id, traits::FnTrait, AliasEq, AliasTy, ClosureId, DomainGoal,
     GenericArg, Goal, ImplTraitId, InEnvironment, Interner, ProjectionTy, RpitId, Substitution,
-    TraitRef, Ty, TyBuilder, TyExt, TyKind,
+    TraitEnvironment, TraitRef, Ty, TyBuilder, TyExt, TyKind,
 };
 
 // This lint has a false positive here. See the link below for details.
@@ -117,11 +117,10 @@ pub(crate) fn infer_query(db: &dyn HirDatabase, def: DefWithBodyId) -> Arc<Infer
 ///
 /// This is appropriate to use only after type-check: it assumes
 /// that normalization will succeed, for example.
-pub(crate) fn normalize(db: &dyn HirDatabase, owner: DefWithBodyId, ty: Ty) -> Ty {
+pub(crate) fn normalize(db: &dyn HirDatabase, trait_env: Arc<TraitEnvironment>, ty: Ty) -> Ty {
     if !ty.data(Interner).flags.intersects(TypeFlags::HAS_PROJECTION) {
         return ty;
     }
-    let trait_env = db.trait_environment_for_body(owner);
     let mut table = unify::InferenceTable::new(db, trait_env);
 
     let ty_with_vars = table.normalize_associated_types_in(ty);
diff --git a/crates/hir-ty/src/infer/closure.rs b/crates/hir-ty/src/infer/closure.rs
index 346c7f6df66..d3acbf7b404 100644
--- a/crates/hir-ty/src/infer/closure.rs
+++ b/crates/hir-ty/src/infer/closure.rs
@@ -2,7 +2,11 @@
 
 use std::{cmp, collections::HashMap, convert::Infallible, mem};
 
-use chalk_ir::{cast::Cast, AliasEq, AliasTy, FnSubst, Mutability, TyKind, WhereClause};
+use chalk_ir::{
+    cast::Cast,
+    fold::{FallibleTypeFolder, TypeFoldable},
+    AliasEq, AliasTy, BoundVar, DebruijnIndex, FnSubst, Mutability, TyKind, WhereClause,
+};
 use hir_def::{
     data::adt::VariantData,
     hir::{
@@ -11,7 +15,7 @@ use hir_def::{
     },
     lang_item::LangItem,
     resolver::{resolver_for_expr, ResolveValueResult, ValueNs},
-    FieldId, HasModule, VariantId,
+    DefWithBodyId, FieldId, HasModule, VariantId,
 };
 use hir_expand::name;
 use rustc_hash::FxHashMap;
@@ -20,12 +24,13 @@ use stdx::never;
 
 use crate::{
     db::HirDatabase,
+    from_placeholder_idx, make_binders,
     mir::{BorrowKind, MirSpan, ProjectionElem},
     static_lifetime, to_chalk_trait_id,
     traits::FnTrait,
-    utils::{self, pattern_matching_dereference_count},
-    Adjust, Adjustment, Canonical, CanonicalVarKinds, ChalkTraitId, ClosureId, DynTy, FnPointer,
-    FnSig, InEnvironment, Interner, Substitution, Ty, TyBuilder, TyExt,
+    utils::{self, generics, pattern_matching_dereference_count, Generics},
+    Adjust, Adjustment, Binders, ChalkTraitId, ClosureId, DynTy, FnPointer, FnSig, Interner,
+    Substitution, Ty, TyExt,
 };
 
 use super::{Expectation, InferenceContext};
@@ -117,7 +122,7 @@ impl HirPlace {
     fn ty(&self, ctx: &mut InferenceContext<'_>) -> Ty {
         let mut ty = ctx.table.resolve_completely(ctx.result[self.local].clone());
         for p in &self.projections {
-            ty = p.projected_ty(ty, ctx.db, |_, _| {
+            ty = p.projected_ty(ty, ctx.db, |_, _, _| {
                 unreachable!("Closure field only happens in MIR");
             });
         }
@@ -152,7 +157,7 @@ pub struct CapturedItem {
     pub(crate) place: HirPlace,
     pub(crate) kind: CaptureKind,
     pub(crate) span: MirSpan,
-    pub(crate) ty: Ty,
+    pub(crate) ty: Binders<Ty>,
 }
 
 impl CapturedItem {
@@ -232,6 +237,52 @@ pub(crate) struct CapturedItemWithoutTy {
 
 impl CapturedItemWithoutTy {
     fn with_ty(self, ctx: &mut InferenceContext<'_>) -> CapturedItem {
+        fn replace_placeholder_with_binder(
+            db: &dyn HirDatabase,
+            owner: DefWithBodyId,
+            ty: Ty,
+        ) -> Binders<Ty> {
+            struct Filler<'a> {
+                db: &'a dyn HirDatabase,
+                generics: Generics,
+            }
+            impl FallibleTypeFolder<Interner> for Filler<'_> {
+                type Error = ();
+
+                fn as_dyn(&mut self) -> &mut dyn FallibleTypeFolder<Interner, Error = Self::Error> {
+                    self
+                }
+
+                fn interner(&self) -> Interner {
+                    Interner
+                }
+
+                fn try_fold_free_placeholder_ty(
+                    &mut self,
+                    idx: chalk_ir::PlaceholderIndex,
+                    _outer_binder: DebruijnIndex,
+                ) -> std::result::Result<Ty, Self::Error> {
+                    let x = from_placeholder_idx(self.db, idx);
+                    let Some(idx) = self.generics.param_idx(x) else {
+                        return Err(());
+                    };
+                    Ok(TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
+                        .intern(Interner))
+                }
+            }
+            let g_def = match owner {
+                DefWithBodyId::FunctionId(f) => Some(f.into()),
+                DefWithBodyId::StaticId(_) => None,
+                DefWithBodyId::ConstId(f) => Some(f.into()),
+                DefWithBodyId::VariantId(f) => Some(f.into()),
+            };
+            let Some(generics) = g_def.map(|g_def| generics(db.upcast(), g_def)) else {
+                return Binders::empty(Interner, ty);
+            };
+            let filler = &mut Filler { db, generics };
+            let result = ty.clone().try_fold_with(filler, DebruijnIndex::INNERMOST).unwrap_or(ty);
+            make_binders(db, &filler.generics, result)
+        }
         let ty = self.place.ty(ctx).clone();
         let ty = match &self.kind {
             CaptureKind::ByValue => ty,
@@ -243,7 +294,12 @@ impl CapturedItemWithoutTy {
                 TyKind::Ref(m, static_lifetime(), ty).intern(Interner)
             }
         };
-        CapturedItem { place: self.place, kind: self.kind, span: self.span, ty }
+        CapturedItem {
+            place: self.place,
+            kind: self.kind,
+            span: self.span,
+            ty: replace_placeholder_with_binder(ctx.db, ctx.owner, ty),
+        }
     }
 }
 
@@ -590,17 +646,7 @@ impl InferenceContext<'_> {
             // without creating query cycles.
             return self.result.closure_info.get(id).map(|x| x.1 == FnTrait::Fn).unwrap_or(true);
         }
-        let crate_id = self.owner.module(self.db.upcast()).krate();
-        let Some(copy_trait) = self.db.lang_item(crate_id, LangItem::Copy).and_then(|x| x.as_trait()) else {
-            return false;
-        };
-        let trait_ref = TyBuilder::trait_ref(self.db, copy_trait).push(ty).build();
-        let env = self.db.trait_environment_for_body(self.owner);
-        let goal = Canonical {
-            value: InEnvironment::new(&env.env, trait_ref.cast(Interner)),
-            binders: CanonicalVarKinds::empty(Interner),
-        };
-        self.db.trait_solve(crate_id, None, goal).is_some()
+        ty.is_copy(self.db, self.owner)
     }
 
     fn select_from_expr(&mut self, expr: ExprId) {
diff --git a/crates/hir-ty/src/infer/coerce.rs b/crates/hir-ty/src/infer/coerce.rs
index 2249d84edbf..d613a5ff504 100644
--- a/crates/hir-ty/src/infer/coerce.rs
+++ b/crates/hir-ty/src/infer/coerce.rs
@@ -21,8 +21,10 @@ use crate::{
         Adjust, Adjustment, AutoBorrow, InferOk, InferenceContext, OverloadedDeref, PointerCast,
         TypeError, TypeMismatch,
     },
-    static_lifetime, Canonical, DomainGoal, FnPointer, FnSig, Guidance, InEnvironment, Interner,
-    Solution, Substitution, TraitEnvironment, Ty, TyBuilder, TyExt,
+    static_lifetime,
+    utils::ClosureSubst,
+    Canonical, DomainGoal, FnPointer, FnSig, Guidance, InEnvironment, Interner, Solution,
+    Substitution, TraitEnvironment, Ty, TyBuilder, TyExt,
 };
 
 use super::unify::InferenceTable;
@@ -670,7 +672,7 @@ impl<'a> InferenceTable<'a> {
 }
 
 fn coerce_closure_fn_ty(closure_substs: &Substitution, safety: chalk_ir::Safety) -> Ty {
-    let closure_sig = closure_substs.at(Interner, 0).assert_ty_ref(Interner).clone();
+    let closure_sig = ClosureSubst(closure_substs).sig_ty().clone();
     match closure_sig.kind(Interner) {
         TyKind::Function(fn_ty) => TyKind::Function(FnPointer {
             num_binders: fn_ty.num_binders,
diff --git a/crates/hir-ty/src/infer/expr.rs b/crates/hir-ty/src/infer/expr.rs
index 2c37d25f54b..06ca9b026e3 100644
--- a/crates/hir-ty/src/infer/expr.rs
+++ b/crates/hir-ty/src/infer/expr.rs
@@ -282,7 +282,7 @@ impl<'a> InferenceContext<'a> {
                         let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
                         let closure_ty = TyKind::Closure(
                             closure_id,
-                            Substitution::from1(Interner, sig_ty.clone()),
+                            TyBuilder::subst_for_closure(self.db, self.owner, sig_ty.clone()),
                         )
                         .intern(Interner);
                         self.deferred_closures.entry(closure_id).or_default();
diff --git a/crates/hir-ty/src/layout.rs b/crates/hir-ty/src/layout.rs
index 512836afbf3..ebbf16caee1 100644
--- a/crates/hir-ty/src/layout.rs
+++ b/crates/hir-ty/src/layout.rs
@@ -1,5 +1,7 @@
 //! Compute the binary representation of a type
 
+use std::sync::Arc;
+
 use base_db::CrateId;
 use chalk_ir::{AdtId, TyKind};
 use hir_def::{
@@ -13,8 +15,8 @@ use la_arena::{Idx, RawIdx};
 use stdx::never;
 
 use crate::{
-    consteval::try_const_usize, db::HirDatabase, layout::adt::struct_variant_idx, Interner,
-    Substitution, Ty,
+    consteval::try_const_usize, db::HirDatabase, infer::normalize, layout::adt::struct_variant_idx,
+    utils::ClosureSubst, Interner, Substitution, TraitEnvironment, Ty,
 };
 
 pub use self::{
@@ -80,6 +82,8 @@ pub fn layout_of_ty(db: &dyn HirDatabase, ty: &Ty, krate: CrateId) -> Result<Lay
     let Some(target) = db.target_data_layout(krate) else { return Err(LayoutError::TargetLayoutNotAvailable) };
     let cx = LayoutCx { krate, target: &target };
     let dl = &*cx.current_data_layout();
+    let trait_env = Arc::new(TraitEnvironment::empty(krate));
+    let ty = normalize(db, trait_env, ty.clone());
     Ok(match ty.kind(Interner) {
         TyKind::Adt(AdtId(def), subst) => db.layout_of_adt(*def, subst.clone())?,
         TyKind::Scalar(s) => match s {
@@ -146,7 +150,7 @@ pub fn layout_of_ty(db: &dyn HirDatabase, ty: &Ty, krate: CrateId) -> Result<Lay
         }
         TyKind::Array(element, count) => {
             let count = try_const_usize(&count).ok_or(LayoutError::UserError(
-                "mismatched type of const generic parameter".to_string(),
+                "unevaluated or mistyped const generic parameter".to_string(),
             ))? as u64;
             let element = layout_of_ty(db, element, krate)?;
             let size = element.size.checked_mul(count, dl).ok_or(LayoutError::SizeOverflow)?;
@@ -252,13 +256,19 @@ pub fn layout_of_ty(db: &dyn HirDatabase, ty: &Ty, krate: CrateId) -> Result<Lay
                 }
             }
         }
-        TyKind::Closure(c, _) => {
+        TyKind::Closure(c, subst) => {
             let (def, _) = db.lookup_intern_closure((*c).into());
             let infer = db.infer(def);
             let (captures, _) = infer.closure_info(c);
             let fields = captures
                 .iter()
-                .map(|x| layout_of_ty(db, &x.ty, krate))
+                .map(|x| {
+                    layout_of_ty(
+                        db,
+                        &x.ty.clone().substitute(Interner, ClosureSubst(subst).parent_subst()),
+                        krate,
+                    )
+                })
                 .collect::<Result<Vec<_>, _>>()?;
             let fields = fields.iter().collect::<Vec<_>>();
             let fields = fields.iter().collect::<Vec<_>>();
diff --git a/crates/hir-ty/src/layout/tests.rs b/crates/hir-ty/src/layout/tests.rs
index 3cd0cd399c4..1502ab14cc7 100644
--- a/crates/hir-ty/src/layout/tests.rs
+++ b/crates/hir-ty/src/layout/tests.rs
@@ -219,6 +219,22 @@ fn generic() {
 }
 
 #[test]
+fn associated_types() {
+    size_and_align! {
+        trait Tr {
+            type Ty;
+        }
+
+        impl Tr for i32 {
+            type Ty = i64;
+        }
+
+        struct Foo<A: Tr>(<A as Tr>::Ty);
+        struct Goal(Foo<i32>);
+    }
+}
+
+#[test]
 fn return_position_impl_trait() {
     size_and_align_expr! {
         trait T {}
diff --git a/crates/hir-ty/src/lib.rs b/crates/hir-ty/src/lib.rs
index e5b356dde6c..071d95839ec 100644
--- a/crates/hir-ty/src/lib.rs
+++ b/crates/hir-ty/src/lib.rs
@@ -44,10 +44,10 @@ use chalk_ir::{
     NoSolution, TyData,
 };
 use either::Either;
-use hir_def::{hir::ExprId, type_ref::Rawness, TypeOrConstParamId};
+use hir_def::{hir::ExprId, type_ref::Rawness, ConstId, TypeOrConstParamId};
 use hir_expand::name;
 use la_arena::{Arena, Idx};
-use mir::MirEvalError;
+use mir::{MirEvalError, VTableMap};
 use rustc_hash::FxHashSet;
 use traits::FnTrait;
 use utils::Generics;
@@ -151,11 +151,14 @@ pub type WhereClause = chalk_ir::WhereClause<Interner>;
 /// the necessary bits of memory of the const eval session to keep the constant
 /// meaningful.
 #[derive(Debug, Default, Clone, PartialEq, Eq)]
-pub struct MemoryMap(pub HashMap<usize, Vec<u8>>);
+pub struct MemoryMap {
+    pub memory: HashMap<usize, Vec<u8>>,
+    pub vtable: VTableMap,
+}
 
 impl MemoryMap {
     fn insert(&mut self, addr: usize, x: Vec<u8>) {
-        self.0.insert(addr, x);
+        self.memory.insert(addr, x);
     }
 
     /// This functions convert each address by a function `f` which gets the byte intervals and assign an address
@@ -165,7 +168,7 @@ impl MemoryMap {
         &self,
         mut f: impl FnMut(&[u8]) -> Result<usize, MirEvalError>,
     ) -> Result<HashMap<usize, usize>, MirEvalError> {
-        self.0.iter().map(|x| Ok((*x.0, f(x.1)?))).collect()
+        self.memory.iter().map(|x| Ok((*x.0, f(x.1)?))).collect()
     }
 }
 
@@ -173,6 +176,9 @@ impl MemoryMap {
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum ConstScalar {
     Bytes(Vec<u8>, MemoryMap),
+    // FIXME: this is a hack to get around chalk not being able to represent unevaluatable
+    // constants
+    UnevaluatedConst(ConstId, Substitution),
     /// Case of an unknown value that rustc might know but we don't
     // FIXME: this is a hack to get around chalk not being able to represent unevaluatable
     // constants
diff --git a/crates/hir-ty/src/mir.rs b/crates/hir-ty/src/mir.rs
index fef00771199..4846bbfe5fd 100644
--- a/crates/hir-ty/src/mir.rs
+++ b/crates/hir-ty/src/mir.rs
@@ -3,13 +3,14 @@
 use std::{fmt::Display, iter};
 
 use crate::{
-    db::HirDatabase, display::HirDisplay, infer::PointerCast, lang_items::is_box, ClosureId, Const,
-    ConstScalar, InferenceResult, Interner, MemoryMap, Substitution, Ty, TyKind,
+    db::HirDatabase, display::HirDisplay, infer::PointerCast, lang_items::is_box, mapping::ToChalk,
+    CallableDefId, ClosureId, Const, ConstScalar, InferenceResult, Interner, MemoryMap,
+    Substitution, Ty, TyKind,
 };
 use chalk_ir::Mutability;
 use hir_def::{
     hir::{BindingId, Expr, ExprId, Ordering, PatId},
-    DefWithBodyId, FieldId, UnionId, VariantId,
+    DefWithBodyId, FieldId, StaticId, UnionId, VariantId,
 };
 use la_arena::{Arena, ArenaMap, Idx, RawIdx};
 
@@ -19,7 +20,7 @@ mod borrowck;
 mod pretty;
 
 pub use borrowck::{borrowck_query, BorrowckResult, MutabilityReason};
-pub use eval::{interpret_mir, pad16, Evaluator, MirEvalError};
+pub use eval::{interpret_mir, pad16, Evaluator, MirEvalError, VTableMap};
 pub use lower::{
     lower_to_mir, mir_body_for_closure_query, mir_body_query, mir_body_recover, MirLowerError,
 };
@@ -76,6 +77,9 @@ pub enum Operand {
     Move(Place),
     /// Constants are already semantically values, and remain unchanged.
     Constant(Const),
+    /// NON STANDARD: This kind of operand returns an immutable reference to that static memory. Rustc
+    /// handles it with the `Constant` variant somehow.
+    Static(StaticId),
 }
 
 impl Operand {
@@ -90,6 +94,17 @@ impl Operand {
     fn const_zst(ty: Ty) -> Operand {
         Self::from_bytes(vec![], ty)
     }
+
+    fn from_fn(
+        db: &dyn HirDatabase,
+        func_id: hir_def::FunctionId,
+        generic_args: Substitution,
+    ) -> Operand {
+        let ty =
+            chalk_ir::TyKind::FnDef(CallableDefId::FunctionId(func_id).to_chalk(db), generic_args)
+                .intern(Interner);
+        Operand::from_bytes(vec![], ty)
+    }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -110,7 +125,7 @@ impl<V, T> ProjectionElem<V, T> {
         &self,
         base: Ty,
         db: &dyn HirDatabase,
-        closure_field: impl FnOnce(ClosureId, usize) -> Ty,
+        closure_field: impl FnOnce(ClosureId, &Substitution, usize) -> Ty,
     ) -> Ty {
         match self {
             ProjectionElem::Deref => match &base.data(Interner).kind {
@@ -142,7 +157,7 @@ impl<V, T> ProjectionElem<V, T> {
                         never!("Out of bound tuple field");
                         TyKind::Error.intern(Interner)
                     }),
-                TyKind::Closure(id, _) => closure_field(*id, *f),
+                TyKind::Closure(id, subst) => closure_field(*id, subst, *f),
                 _ => {
                     never!("Only tuple or closure has tuple or closure field");
                     return TyKind::Error.intern(Interner);
@@ -261,7 +276,13 @@ impl SwitchTargets {
 }
 
 #[derive(Debug, PartialEq, Eq, Clone)]
-pub enum Terminator {
+pub struct Terminator {
+    span: MirSpan,
+    kind: TerminatorKind,
+}
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub enum TerminatorKind {
     /// Block has one successor; we continue execution there.
     Goto { target: BasicBlockId },
 
@@ -836,6 +857,9 @@ pub enum Rvalue {
     /// affects alias analysis.
     ShallowInitBox(Operand, Ty),
 
+    /// NON STANDARD: allocates memory with the type's layout, and shallow init the box with the resulting pointer.
+    ShallowInitBoxWithAlloc(Ty),
+
     /// A CopyForDeref is equivalent to a read from a place at the
     /// codegen level, but is treated specially by drop elaboration. When such a read happens, it
     /// is guaranteed (via nature of the mir_opt `Derefer` in rustc_mir_transform/src/deref_separator)
@@ -918,7 +942,7 @@ impl MirBody {
                 Operand::Copy(p) | Operand::Move(p) => {
                     f(p);
                 }
-                Operand::Constant(_) => (),
+                Operand::Constant(_) | Operand::Static(_) => (),
             }
         }
         for (_, block) in self.basic_blocks.iter_mut() {
@@ -927,6 +951,7 @@ impl MirBody {
                     StatementKind::Assign(p, r) => {
                         f(p);
                         match r {
+                            Rvalue::ShallowInitBoxWithAlloc(_) => (),
                             Rvalue::ShallowInitBox(o, _)
                             | Rvalue::UnaryOp(_, o)
                             | Rvalue::Cast(_, o, _)
@@ -954,32 +979,32 @@ impl MirBody {
                 }
             }
             match &mut block.terminator {
-                Some(x) => match x {
-                    Terminator::SwitchInt { discr, .. } => for_operand(discr, &mut f),
-                    Terminator::FalseEdge { .. }
-                    | Terminator::FalseUnwind { .. }
-                    | Terminator::Goto { .. }
-                    | Terminator::Resume
-                    | Terminator::GeneratorDrop
-                    | Terminator::Abort
-                    | Terminator::Return
-                    | Terminator::Unreachable => (),
-                    Terminator::Drop { place, .. } => {
+                Some(x) => match &mut x.kind {
+                    TerminatorKind::SwitchInt { discr, .. } => for_operand(discr, &mut f),
+                    TerminatorKind::FalseEdge { .. }
+                    | TerminatorKind::FalseUnwind { .. }
+                    | TerminatorKind::Goto { .. }
+                    | TerminatorKind::Resume
+                    | TerminatorKind::GeneratorDrop
+                    | TerminatorKind::Abort
+                    | TerminatorKind::Return
+                    | TerminatorKind::Unreachable => (),
+                    TerminatorKind::Drop { place, .. } => {
                         f(place);
                     }
-                    Terminator::DropAndReplace { place, value, .. } => {
+                    TerminatorKind::DropAndReplace { place, value, .. } => {
                         f(place);
                         for_operand(value, &mut f);
                     }
-                    Terminator::Call { func, args, destination, .. } => {
+                    TerminatorKind::Call { func, args, destination, .. } => {
                         for_operand(func, &mut f);
                         args.iter_mut().for_each(|x| for_operand(x, &mut f));
                         f(destination);
                     }
-                    Terminator::Assert { cond, .. } => {
+                    TerminatorKind::Assert { cond, .. } => {
                         for_operand(cond, &mut f);
                     }
-                    Terminator::Yield { value, resume_arg, .. } => {
+                    TerminatorKind::Yield { value, resume_arg, .. } => {
                         for_operand(value, &mut f);
                         f(resume_arg);
                     }
diff --git a/crates/hir-ty/src/mir/borrowck.rs b/crates/hir-ty/src/mir/borrowck.rs
index 016090d509b..7b99fbf42f0 100644
--- a/crates/hir-ty/src/mir/borrowck.rs
+++ b/crates/hir-ty/src/mir/borrowck.rs
@@ -13,7 +13,7 @@ use crate::{db::HirDatabase, ClosureId};
 
 use super::{
     BasicBlockId, BorrowKind, LocalId, MirBody, MirLowerError, MirSpan, Place, ProjectionElem,
-    Rvalue, StatementKind, Terminator,
+    Rvalue, StatementKind, TerminatorKind,
 };
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -141,26 +141,26 @@ fn ever_initialized_map(body: &MirBody) -> ArenaMap<BasicBlockId, ArenaMap<Local
             never!("Terminator should be none only in construction");
             return;
         };
-        let targets = match terminator {
-            Terminator::Goto { target } => vec![*target],
-            Terminator::SwitchInt { targets, .. } => targets.all_targets().to_vec(),
-            Terminator::Resume
-            | Terminator::Abort
-            | Terminator::Return
-            | Terminator::Unreachable => vec![],
-            Terminator::Call { target, cleanup, destination, .. } => {
+        let targets = match &terminator.kind {
+            TerminatorKind::Goto { target } => vec![*target],
+            TerminatorKind::SwitchInt { targets, .. } => targets.all_targets().to_vec(),
+            TerminatorKind::Resume
+            | TerminatorKind::Abort
+            | TerminatorKind::Return
+            | TerminatorKind::Unreachable => vec![],
+            TerminatorKind::Call { target, cleanup, destination, .. } => {
                 if destination.projection.len() == 0 && destination.local == l {
                     is_ever_initialized = true;
                 }
                 target.into_iter().chain(cleanup.into_iter()).copied().collect()
             }
-            Terminator::Drop { .. }
-            | Terminator::DropAndReplace { .. }
-            | Terminator::Assert { .. }
-            | Terminator::Yield { .. }
-            | Terminator::GeneratorDrop
-            | Terminator::FalseEdge { .. }
-            | Terminator::FalseUnwind { .. } => {
+            TerminatorKind::Drop { .. }
+            | TerminatorKind::DropAndReplace { .. }
+            | TerminatorKind::Assert { .. }
+            | TerminatorKind::Yield { .. }
+            | TerminatorKind::GeneratorDrop
+            | TerminatorKind::FalseEdge { .. }
+            | TerminatorKind::FalseUnwind { .. } => {
                 never!("We don't emit these MIR terminators yet");
                 vec![]
             }
@@ -228,21 +228,21 @@ fn mutability_of_locals(body: &MirBody) -> ArenaMap<LocalId, MutabilityReason> {
             never!("Terminator should be none only in construction");
             continue;
         };
-        match terminator {
-            Terminator::Goto { .. }
-            | Terminator::Resume
-            | Terminator::Abort
-            | Terminator::Return
-            | Terminator::Unreachable
-            | Terminator::FalseEdge { .. }
-            | Terminator::FalseUnwind { .. }
-            | Terminator::GeneratorDrop
-            | Terminator::SwitchInt { .. }
-            | Terminator::Drop { .. }
-            | Terminator::DropAndReplace { .. }
-            | Terminator::Assert { .. }
-            | Terminator::Yield { .. } => (),
-            Terminator::Call { destination, .. } => {
+        match &terminator.kind {
+            TerminatorKind::Goto { .. }
+            | TerminatorKind::Resume
+            | TerminatorKind::Abort
+            | TerminatorKind::Return
+            | TerminatorKind::Unreachable
+            | TerminatorKind::FalseEdge { .. }
+            | TerminatorKind::FalseUnwind { .. }
+            | TerminatorKind::GeneratorDrop
+            | TerminatorKind::SwitchInt { .. }
+            | TerminatorKind::Drop { .. }
+            | TerminatorKind::DropAndReplace { .. }
+            | TerminatorKind::Assert { .. }
+            | TerminatorKind::Yield { .. } => (),
+            TerminatorKind::Call { destination, .. } => {
                 if destination.projection.len() == 0 {
                     if ever_init_map.get(destination.local).copied().unwrap_or_default() {
                         push_mut_span(destination.local, MirSpan::Unknown);
diff --git a/crates/hir-ty/src/mir/eval.rs b/crates/hir-ty/src/mir/eval.rs
index bb33da97e33..01d27f2672c 100644
--- a/crates/hir-ty/src/mir/eval.rs
+++ b/crates/hir-ty/src/mir/eval.rs
@@ -1,39 +1,49 @@
 //! This module provides a MIR interpreter, which is used in const eval.
 
-use std::{borrow::Cow, collections::HashMap, iter, ops::Range, sync::Arc};
+use std::{borrow::Cow, collections::HashMap, fmt::Write, iter, ops::Range, sync::Arc};
 
-use base_db::CrateId;
+use base_db::{CrateId, FileId};
 use chalk_ir::{
     fold::{FallibleTypeFolder, TypeFoldable, TypeSuperFoldable},
-    DebruijnIndex, TyKind,
+    DebruijnIndex, Mutability,
 };
+use either::Either;
 use hir_def::{
     builtin_type::BuiltinType,
     lang_item::{lang_attr, LangItem},
     layout::{TagEncoding, Variants},
-    AdtId, DefWithBodyId, EnumVariantId, FunctionId, HasModule, ItemContainerId, Lookup, VariantId,
+    AdtId, DefWithBodyId, EnumVariantId, FunctionId, HasModule, ItemContainerId, Lookup, StaticId,
+    TypeOrConstParamId, VariantId,
 };
+use hir_expand::{name::Name, InFile};
 use intern::Interned;
 use la_arena::ArenaMap;
+use rustc_hash::FxHashMap;
+use syntax::{SyntaxNodePtr, TextRange};
 
 use crate::{
     consteval::{intern_const_scalar, ConstEvalError},
     db::HirDatabase,
+    display::{ClosureStyle, HirDisplay},
     from_placeholder_idx,
     infer::{normalize, PointerCast},
     layout::{layout_of_ty, Layout, LayoutError, RustcEnumVariantIdx},
     mapping::from_chalk,
-    method_resolution::{is_dyn_method, lookup_impl_method},
+    method_resolution::{is_dyn_method, lookup_impl_const, lookup_impl_method},
+    static_lifetime,
     traits::FnTrait,
+    utils::{generics, ClosureSubst, Generics},
     CallableDefId, ClosureId, Const, ConstScalar, FnDefId, GenericArgData, Interner, MemoryMap,
-    Substitution, TraitEnvironment, Ty, TyBuilder, TyExt,
+    Substitution, TraitEnvironment, Ty, TyBuilder, TyExt, TyKind,
 };
 
 use super::{
     const_as_usize, return_slot, AggregateKind, BinOp, CastKind, LocalId, MirBody, MirLowerError,
-    Operand, Place, ProjectionElem, Rvalue, StatementKind, Terminator, UnOp,
+    MirSpan, Operand, Place, ProjectionElem, Rvalue, StatementKind, TerminatorKind, UnOp,
 };
 
+mod shim;
+
 macro_rules! from_bytes {
     ($ty:tt, $value:expr) => {
         ($ty::from_le_bytes(match ($value).try_into() {
@@ -43,9 +53,15 @@ macro_rules! from_bytes {
     };
 }
 
-#[derive(Debug, Default)]
-struct VTableMap {
-    ty_to_id: HashMap<Ty, usize>,
+macro_rules! not_supported {
+    ($x: expr) => {
+        return Err(MirEvalError::NotSupported(format!($x)))
+    };
+}
+
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
+pub struct VTableMap {
+    ty_to_id: FxHashMap<Ty, usize>,
     id_to_ty: Vec<Ty>,
 }
 
@@ -75,6 +91,9 @@ pub struct Evaluator<'a> {
     trait_env: Arc<TraitEnvironment>,
     stack: Vec<u8>,
     heap: Vec<u8>,
+    /// Stores the global location of the statics. We const evaluate every static first time we need it
+    /// and see it's missing, then we add it to this to reuse.
+    static_locations: FxHashMap<StaticId, Address>,
     /// We don't really have function pointers, i.e. pointers to some assembly instructions that we can run. Instead, we
     /// store the type as an interned id in place of function and vtable pointers, and we recover back the type at the
     /// time of use.
@@ -88,7 +107,7 @@ pub struct Evaluator<'a> {
     stack_depth_limit: usize,
 }
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 enum Address {
     Stack(usize),
     Heap(usize),
@@ -153,6 +172,13 @@ enum IntervalOrOwned {
     Owned(Vec<u8>),
     Borrowed(Interval),
 }
+
+impl From<Interval> for IntervalOrOwned {
+    fn from(it: Interval) -> IntervalOrOwned {
+        IntervalOrOwned::Borrowed(it)
+    }
+}
+
 impl IntervalOrOwned {
     pub(crate) fn to_vec(self, memory: &Evaluator<'_>) -> Result<Vec<u8>> {
         Ok(match self {
@@ -160,6 +186,13 @@ impl IntervalOrOwned {
             IntervalOrOwned::Borrowed(b) => b.get(memory)?.to_vec(),
         })
     }
+
+    fn get<'a>(&'a self, memory: &'a Evaluator<'a>) -> Result<&'a [u8]> {
+        Ok(match self {
+            IntervalOrOwned::Owned(o) => o,
+            IntervalOrOwned::Borrowed(b) => b.get(memory)?,
+        })
+    }
 }
 
 impl Address {
@@ -205,30 +238,129 @@ impl Address {
 
 #[derive(Clone, PartialEq, Eq)]
 pub enum MirEvalError {
-    ConstEvalError(Box<ConstEvalError>),
+    ConstEvalError(String, Box<ConstEvalError>),
     LayoutError(LayoutError, Ty),
     /// Means that code had type errors (or mismatched args) and we shouldn't generate mir in first place.
     TypeError(&'static str),
     /// Means that code had undefined behavior. We don't try to actively detect UB, but if it was detected
     /// then use this type of error.
-    UndefinedBehavior(&'static str),
+    UndefinedBehavior(String),
+    GenericArgNotProvided(TypeOrConstParamId, Substitution),
     Panic(String),
     MirLowerError(FunctionId, MirLowerError),
     MirLowerErrorForClosure(ClosureId, MirLowerError),
     TypeIsUnsized(Ty, &'static str),
     NotSupported(String),
     InvalidConst(Const),
-    InFunction(FunctionId, Box<MirEvalError>),
+    InFunction(Either<FunctionId, ClosureId>, Box<MirEvalError>, MirSpan, DefWithBodyId),
     ExecutionLimitExceeded,
     StackOverflow,
     TargetDataLayoutNotAvailable,
     InvalidVTableId(usize),
+    CoerceUnsizedError(Ty),
+}
+
+impl MirEvalError {
+    pub fn pretty_print(
+        &self,
+        f: &mut String,
+        db: &dyn HirDatabase,
+        span_formatter: impl Fn(FileId, TextRange) -> String,
+    ) -> std::result::Result<(), std::fmt::Error> {
+        writeln!(f, "Mir eval error:")?;
+        let mut err = self;
+        while let MirEvalError::InFunction(func, e, span, def) = err {
+            err = e;
+            match func {
+                Either::Left(func) => {
+                    let function_name = db.function_data(*func);
+                    writeln!(f, "In function {} ({:?})", function_name.name, func)?;
+                }
+                Either::Right(clos) => {
+                    writeln!(f, "In {:?}", clos)?;
+                }
+            }
+            let source_map = db.body_with_source_map(*def).1;
+            let span: InFile<SyntaxNodePtr> = match span {
+                MirSpan::ExprId(e) => match source_map.expr_syntax(*e) {
+                    Ok(s) => s.map(|x| x.into()),
+                    Err(_) => continue,
+                },
+                MirSpan::PatId(p) => match source_map.pat_syntax(*p) {
+                    Ok(s) => s.map(|x| match x {
+                        Either::Left(e) => e.into(),
+                        Either::Right(e) => e.into(),
+                    }),
+                    Err(_) => continue,
+                },
+                MirSpan::Unknown => continue,
+            };
+            let file_id = span.file_id.original_file(db.upcast());
+            let text_range = span.value.text_range();
+            writeln!(f, "{}", span_formatter(file_id, text_range))?;
+        }
+        match err {
+            MirEvalError::InFunction(..) => unreachable!(),
+            MirEvalError::LayoutError(err, ty) => {
+                write!(
+                    f,
+                    "Layout for type `{}` is not available due {err:?}",
+                    ty.display(db).with_closure_style(ClosureStyle::ClosureWithId).to_string()
+                )?;
+            }
+            MirEvalError::GenericArgNotProvided(id, subst) => {
+                let parent = id.parent;
+                let param = &db.generic_params(parent).type_or_consts[id.local_id];
+                writeln!(
+                    f,
+                    "Generic arg not provided for {}",
+                    param.name().unwrap_or(&Name::missing())
+                )?;
+                writeln!(f, "Provided args: [")?;
+                for g in subst.iter(Interner) {
+                    write!(f, "    {},", g.display(db).to_string())?;
+                }
+                writeln!(f, "]")?;
+            }
+            MirEvalError::MirLowerError(func, err) => {
+                let function_name = db.function_data(*func);
+                writeln!(
+                    f,
+                    "MIR lowering for function `{}` ({:?}) failed due:",
+                    function_name.name, func
+                )?;
+                err.pretty_print(f, db, span_formatter)?;
+            }
+            MirEvalError::ConstEvalError(name, err) => {
+                MirLowerError::ConstEvalError(name.clone(), err.clone()).pretty_print(
+                    f,
+                    db,
+                    span_formatter,
+                )?;
+            }
+            MirEvalError::TypeError(_)
+            | MirEvalError::UndefinedBehavior(_)
+            | MirEvalError::Panic(_)
+            | MirEvalError::MirLowerErrorForClosure(_, _)
+            | MirEvalError::TypeIsUnsized(_, _)
+            | MirEvalError::NotSupported(_)
+            | MirEvalError::InvalidConst(_)
+            | MirEvalError::ExecutionLimitExceeded
+            | MirEvalError::StackOverflow
+            | MirEvalError::TargetDataLayoutNotAvailable
+            | MirEvalError::CoerceUnsizedError(_)
+            | MirEvalError::InvalidVTableId(_) => writeln!(f, "{:?}", err)?,
+        }
+        Ok(())
+    }
 }
 
 impl std::fmt::Debug for MirEvalError {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Self::ConstEvalError(arg0) => f.debug_tuple("ConstEvalError").field(arg0).finish(),
+            Self::ConstEvalError(arg0, arg1) => {
+                f.debug_tuple("ConstEvalError").field(arg0).field(arg1).finish()
+            }
             Self::LayoutError(arg0, arg1) => {
                 f.debug_tuple("LayoutError").field(arg0).field(arg1).finish()
             }
@@ -241,24 +373,28 @@ impl std::fmt::Debug for MirEvalError {
             Self::TypeIsUnsized(ty, it) => write!(f, "{ty:?} is unsized. {it} should be sized."),
             Self::ExecutionLimitExceeded => write!(f, "execution limit exceeded"),
             Self::StackOverflow => write!(f, "stack overflow"),
+            Self::GenericArgNotProvided(..) => f.debug_tuple("GenericArgNotProvided").finish(),
             Self::MirLowerError(arg0, arg1) => {
                 f.debug_tuple("MirLowerError").field(arg0).field(arg1).finish()
             }
             Self::MirLowerErrorForClosure(arg0, arg1) => {
                 f.debug_tuple("MirLowerError").field(arg0).field(arg1).finish()
             }
+            Self::CoerceUnsizedError(arg0) => {
+                f.debug_tuple("CoerceUnsizedError").field(arg0).finish()
+            }
             Self::InvalidVTableId(arg0) => f.debug_tuple("InvalidVTableId").field(arg0).finish(),
             Self::NotSupported(arg0) => f.debug_tuple("NotSupported").field(arg0).finish(),
             Self::InvalidConst(arg0) => {
                 let data = &arg0.data(Interner);
                 f.debug_struct("InvalidConst").field("ty", &data.ty).field("value", &arg0).finish()
             }
-            Self::InFunction(func, e) => {
+            Self::InFunction(func, e, span, _) => {
                 let mut e = &**e;
-                let mut stack = vec![*func];
-                while let Self::InFunction(f, next_e) = e {
+                let mut stack = vec![(*func, *span)];
+                while let Self::InFunction(f, next_e, span, _) = e {
                     e = &next_e;
-                    stack.push(*f);
+                    stack.push((*f, *span));
                 }
                 f.debug_struct("WithStack").field("error", e).field("stack", &stack).finish()
             }
@@ -266,22 +402,9 @@ impl std::fmt::Debug for MirEvalError {
     }
 }
 
-macro_rules! not_supported {
-    ($x: expr) => {
-        return Err(MirEvalError::NotSupported(format!($x)))
-    };
-}
-
-impl From<ConstEvalError> for MirEvalError {
-    fn from(value: ConstEvalError) -> Self {
-        match value {
-            _ => MirEvalError::ConstEvalError(Box::new(value)),
-        }
-    }
-}
-
 type Result<T> = std::result::Result<T, MirEvalError>;
 
+#[derive(Debug)]
 struct Locals<'a> {
     ptr: &'a ArenaMap<LocalId, Address>,
     body: &'a MirBody,
@@ -301,12 +424,14 @@ pub fn interpret_mir(
 ) -> Result<Const> {
     let ty = body.locals[return_slot()].ty.clone();
     let mut evaluator = Evaluator::new(db, body, assert_placeholder_ty_is_unused);
+    let ty = evaluator.ty_filler(&ty, &subst, body.owner)?;
     let bytes = evaluator.interpret_mir(&body, None.into_iter(), subst.clone())?;
-    let memory_map = evaluator.create_memory_map(
+    let mut memory_map = evaluator.create_memory_map(
         &bytes,
         &ty,
         &Locals { ptr: &ArenaMap::new(), body: &body, subst: &subst },
     )?;
+    memory_map.vtable = evaluator.vtable_map;
     return Ok(intern_const_scalar(ConstScalar::Bytes(bytes, memory_map), ty));
 }
 
@@ -322,6 +447,7 @@ impl Evaluator<'_> {
             stack: vec![0],
             heap: vec![0],
             vtable_map: VTableMap::default(),
+            static_locations: HashMap::default(),
             db,
             trait_env,
             crate_id,
@@ -365,15 +491,21 @@ impl Evaluator<'_> {
         let mut metadata = None; // locals are always sized
         for proj in &p.projection {
             let prev_ty = ty.clone();
-            ty = proj.projected_ty(ty, self.db, |c, f| {
+            ty = proj.projected_ty(ty, self.db, |c, subst, f| {
                 let (def, _) = self.db.lookup_intern_closure(c.into());
                 let infer = self.db.infer(def);
                 let (captures, _) = infer.closure_info(&c);
-                captures.get(f).expect("broken closure field").ty.clone()
+                let parent_subst = ClosureSubst(subst).parent_subst();
+                captures
+                    .get(f)
+                    .expect("broken closure field")
+                    .ty
+                    .clone()
+                    .substitute(Interner, parent_subst)
             });
             match proj {
                 ProjectionElem::Deref => {
-                    metadata = if self.size_of(&ty, locals)?.is_none() {
+                    metadata = if self.size_align_of(&ty, locals)?.is_none() {
                         Some(Interval { addr: addr.offset(self.ptr_size()), size: self.ptr_size() })
                     } else {
                         None
@@ -435,6 +567,11 @@ impl Evaluator<'_> {
             .map_err(|e| MirEvalError::LayoutError(e, ty.clone()))
     }
 
+    fn layout_filled(&self, ty: &Ty, locals: &Locals<'_>) -> Result<Layout> {
+        let ty = &self.ty_filler(ty, locals.subst, locals.body.owner)?;
+        self.layout(ty)
+    }
+
     fn layout_adt(&self, adt: AdtId, subst: Substitution) -> Result<Layout> {
         self.db.layout_of_adt(adt, subst.clone()).map_err(|e| {
             MirEvalError::LayoutError(e, TyKind::Adt(chalk_ir::AdtId(adt), subst).intern(Interner))
@@ -449,6 +586,10 @@ impl Evaluator<'_> {
         Ok(match o {
             Operand::Copy(p) | Operand::Move(p) => self.place_ty(p, locals)?,
             Operand::Constant(c) => c.data(Interner).ty.clone(),
+            &Operand::Static(s) => {
+                let ty = self.db.infer(s.into())[self.db.body(s.into()).body_expr].clone();
+                TyKind::Ref(Mutability::Not, static_lifetime(), ty).intern(Interner)
+            }
         })
     }
 
@@ -524,11 +665,11 @@ impl Evaluator<'_> {
             let Some(terminator) = current_block.terminator.as_ref() else {
                 not_supported!("block without terminator");
             };
-            match terminator {
-                Terminator::Goto { target } => {
+            match &terminator.kind {
+                TerminatorKind::Goto { target } => {
                     current_block_idx = *target;
                 }
-                Terminator::Call {
+                TerminatorKind::Call {
                     func,
                     args,
                     destination,
@@ -545,23 +686,36 @@ impl Evaluator<'_> {
                     match &fn_ty.data(Interner).kind {
                         TyKind::Function(_) => {
                             let bytes = self.eval_operand(func, &locals)?;
-                            self.exec_fn_pointer(bytes, destination, &args, &locals)?;
+                            self.exec_fn_pointer(
+                                bytes,
+                                destination,
+                                &args,
+                                &locals,
+                                terminator.span,
+                            )?;
                         }
                         TyKind::FnDef(def, generic_args) => {
-                            self.exec_fn_def(*def, generic_args, destination, &args, &locals)?;
+                            self.exec_fn_def(
+                                *def,
+                                generic_args,
+                                destination,
+                                &args,
+                                &locals,
+                                terminator.span,
+                            )?;
                         }
                         x => not_supported!("unknown function type {x:?}"),
                     }
                     current_block_idx = target.expect("broken mir, function without target");
                 }
-                Terminator::SwitchInt { discr, targets } => {
+                TerminatorKind::SwitchInt { discr, targets } => {
                     let val = u128::from_le_bytes(pad16(
                         self.eval_operand(discr, &locals)?.get(&self)?,
                         false,
                     ));
                     current_block_idx = targets.target_for_value(val);
                 }
-                Terminator::Return => {
+                TerminatorKind::Return => {
                     let ty = body.locals[return_slot()].ty.clone();
                     self.stack_depth_limit += 1;
                     return Ok(self
@@ -571,8 +725,8 @@ impl Evaluator<'_> {
                         )?
                         .to_owned());
                 }
-                Terminator::Unreachable => {
-                    return Err(MirEvalError::UndefinedBehavior("unreachable executed"));
+                TerminatorKind::Unreachable => {
+                    return Err(MirEvalError::UndefinedBehavior("unreachable executed".to_owned()));
                 }
                 _ => not_supported!("unknown terminator"),
             }
@@ -725,13 +879,13 @@ impl Evaluator<'_> {
                 };
                 match layout.variants {
                     Variants::Single { index } => {
-                        let r = self.db.const_eval_discriminant(EnumVariantId {
+                        let r = self.const_eval_discriminant(EnumVariantId {
                             parent: enum_id,
                             local_id: index.0,
                         })?;
                         Owned(r.to_le_bytes().to_vec())
                     }
-                    Variants::Multiple { tag, tag_encoding, .. } => {
+                    Variants::Multiple { tag, tag_encoding, variants, .. } => {
                         let Some(target_data_layout) = self.db.target_data_layout(self.crate_id) else {
                             not_supported!("missing target data layout");
                         };
@@ -744,25 +898,20 @@ impl Evaluator<'_> {
                             }
                             TagEncoding::Niche { untagged_variant, niche_start, .. } => {
                                 let tag = &bytes[offset..offset + size];
-                                let candidate_discriminant = i128::from_le_bytes(pad16(tag, false))
-                                    .wrapping_sub(niche_start as i128);
-                                let enum_data = self.db.enum_data(enum_id);
-                                let result = 'b: {
-                                    for (local_id, _) in enum_data.variants.iter() {
-                                        if candidate_discriminant
-                                            == self.db.const_eval_discriminant(EnumVariantId {
-                                                parent: enum_id,
-                                                local_id,
-                                            })?
-                                        {
-                                            break 'b candidate_discriminant;
-                                        }
-                                    }
-                                    self.db.const_eval_discriminant(EnumVariantId {
-                                        parent: enum_id,
-                                        local_id: untagged_variant.0,
-                                    })?
-                                };
+                                let candidate_tag = i128::from_le_bytes(pad16(tag, false))
+                                    .wrapping_sub(niche_start as i128)
+                                    as usize;
+                                let variant = variants
+                                    .iter_enumerated()
+                                    .map(|(x, _)| x)
+                                    .filter(|x| *x != untagged_variant)
+                                    .nth(candidate_tag)
+                                    .unwrap_or(untagged_variant)
+                                    .0;
+                                let result = self.const_eval_discriminant(EnumVariantId {
+                                    parent: enum_id,
+                                    local_id: variant,
+                                })?;
                                 Owned(result.to_le_bytes().to_vec())
                             }
                         }
@@ -771,6 +920,13 @@ impl Evaluator<'_> {
             }
             Rvalue::Repeat(_, _) => not_supported!("evaluating repeat rvalue"),
             Rvalue::ShallowInitBox(_, _) => not_supported!("shallow init box"),
+            Rvalue::ShallowInitBoxWithAlloc(ty) => {
+                let Some((size, align)) = self.size_align_of(ty, locals)? else {
+                    not_supported!("unsized box initialization");
+                };
+                let addr = self.heap_allocate(size, align);
+                Owned(addr.to_bytes())
+            }
             Rvalue::CopyForDeref(_) => not_supported!("copy for deref"),
             Rvalue::Aggregate(kind, values) => {
                 let values = values
@@ -787,12 +943,12 @@ impl Evaluator<'_> {
                         Owned(r)
                     }
                     AggregateKind::Tuple(ty) => {
-                        let layout = self.layout(&ty)?;
+                        let layout = self.layout_filled(&ty, locals)?;
                         Owned(self.make_by_layout(
                             layout.size.bytes_usize(),
                             &layout,
                             None,
-                            values.iter().copied(),
+                            values.iter().map(|&x| x.into()),
                         )?)
                     }
                     AggregateKind::Union(x, f) => {
@@ -814,74 +970,44 @@ impl Evaluator<'_> {
                             size,
                             &variant_layout,
                             tag,
-                            values.iter().copied(),
+                            values.iter().map(|&x| x.into()),
                         )?)
                     }
                     AggregateKind::Closure(ty) => {
-                        let layout = self.layout(&ty)?;
+                        let layout = self.layout_filled(&ty, locals)?;
                         Owned(self.make_by_layout(
                             layout.size.bytes_usize(),
                             &layout,
                             None,
-                            values.iter().copied(),
+                            values.iter().map(|&x| x.into()),
                         )?)
                     }
                 }
             }
             Rvalue::Cast(kind, operand, target_ty) => match kind {
                 CastKind::Pointer(cast) => match cast {
-                    PointerCast::ReifyFnPointer => {
+                    PointerCast::ReifyFnPointer | PointerCast::ClosureFnPointer(_) => {
                         let current_ty = self.operand_ty(operand, locals)?;
-                        if let TyKind::FnDef(_, _) = &current_ty.data(Interner).kind {
+                        if let TyKind::FnDef(_, _) | TyKind::Closure(_, _) =
+                            &current_ty.data(Interner).kind
+                        {
                             let id = self.vtable_map.id(current_ty);
                             let ptr_size = self.ptr_size();
                             Owned(id.to_le_bytes()[0..ptr_size].to_vec())
                         } else {
-                            not_supported!("ReifyFnPointer cast of a non FnDef type");
+                            not_supported!(
+                                "creating a fn pointer from a non FnDef or Closure type"
+                            );
                         }
                     }
                     PointerCast::Unsize => {
                         let current_ty = self.operand_ty(operand, locals)?;
-                        match &target_ty.data(Interner).kind {
-                            TyKind::Raw(_, ty) | TyKind::Ref(_, _, ty) => {
-                                match &ty.data(Interner).kind {
-                                    TyKind::Slice(_) => match &current_ty.data(Interner).kind {
-                                        TyKind::Raw(_, ty) | TyKind::Ref(_, _, ty) => {
-                                            match &ty.data(Interner).kind {
-                                                TyKind::Array(_, size) => {
-                                                    let addr = self
-                                                        .eval_operand(operand, locals)?
-                                                        .get(&self)?;
-                                                    let len = const_as_usize(size);
-                                                    let mut r = Vec::with_capacity(16);
-                                                    r.extend(addr.iter().copied());
-                                                    r.extend(len.to_le_bytes().into_iter());
-                                                    Owned(r)
-                                                }
-                                                _ => {
-                                                    not_supported!("slice unsizing from non arrays")
-                                                }
-                                            }
-                                        }
-                                        _ => not_supported!("slice unsizing from non pointers"),
-                                    },
-                                    TyKind::Dyn(_) => match &current_ty.data(Interner).kind {
-                                        TyKind::Raw(_, ty) | TyKind::Ref(_, _, ty) => {
-                                            let vtable = self.vtable_map.id(ty.clone());
-                                            let addr =
-                                                self.eval_operand(operand, locals)?.get(&self)?;
-                                            let mut r = Vec::with_capacity(16);
-                                            r.extend(addr.iter().copied());
-                                            r.extend(vtable.to_le_bytes().into_iter());
-                                            Owned(r)
-                                        }
-                                        _ => not_supported!("dyn unsizing from non pointers"),
-                                    },
-                                    _ => not_supported!("unknown unsized cast"),
-                                }
-                            }
-                            _ => not_supported!("unsized cast on unknown pointer type"),
-                        }
+                        let addr = self.eval_operand(operand, locals)?;
+                        self.coerce_unsized(addr, &current_ty, target_ty)?
+                    }
+                    PointerCast::MutToConstPointer | PointerCast::UnsafeFnPointer => {
+                        // This is no-op
+                        Borrowed(self.eval_operand(operand, locals)?)
                     }
                     x => not_supported!("pointer cast {x:?}"),
                 },
@@ -909,6 +1035,77 @@ impl Evaluator<'_> {
         })
     }
 
+    fn coerce_unsized_look_through_fields<T>(
+        &self,
+        ty: &Ty,
+        goal: impl Fn(&TyKind) -> Option<T>,
+    ) -> Result<T> {
+        let kind = ty.kind(Interner);
+        if let Some(x) = goal(kind) {
+            return Ok(x);
+        }
+        if let TyKind::Adt(id, subst) = kind {
+            if let AdtId::StructId(struct_id) = id.0 {
+                let field_types = self.db.field_types(struct_id.into());
+                let mut field_types = field_types.iter();
+                if let Some(ty) =
+                    field_types.next().map(|x| x.1.clone().substitute(Interner, subst))
+                {
+                    return self.coerce_unsized_look_through_fields(&ty, goal);
+                }
+            }
+        }
+        Err(MirEvalError::CoerceUnsizedError(ty.clone()))
+    }
+
+    fn coerce_unsized(
+        &mut self,
+        addr: Interval,
+        current_ty: &Ty,
+        target_ty: &Ty,
+    ) -> Result<IntervalOrOwned> {
+        use IntervalOrOwned::*;
+        fn for_ptr(x: &TyKind) -> Option<Ty> {
+            match x {
+                TyKind::Raw(_, ty) | TyKind::Ref(_, _, ty) => Some(ty.clone()),
+                _ => None,
+            }
+        }
+        Ok(match self.coerce_unsized_look_through_fields(target_ty, for_ptr)? {
+            ty => match &ty.data(Interner).kind {
+                TyKind::Slice(_) => {
+                    match self.coerce_unsized_look_through_fields(current_ty, for_ptr)? {
+                        ty => match &ty.data(Interner).kind {
+                            TyKind::Array(_, size) => {
+                                let len = const_as_usize(size);
+                                let mut r = Vec::with_capacity(16);
+                                let addr = addr.get(self)?;
+                                r.extend(addr.iter().copied());
+                                r.extend(len.to_le_bytes().into_iter());
+                                Owned(r)
+                            }
+                            _ => {
+                                not_supported!("slice unsizing from non arrays")
+                            }
+                        },
+                    }
+                }
+                TyKind::Dyn(_) => match &current_ty.data(Interner).kind {
+                    TyKind::Raw(_, ty) | TyKind::Ref(_, _, ty) => {
+                        let vtable = self.vtable_map.id(ty.clone());
+                        let mut r = Vec::with_capacity(16);
+                        let addr = addr.get(self)?;
+                        r.extend(addr.iter().copied());
+                        r.extend(vtable.to_le_bytes().into_iter());
+                        Owned(r)
+                    }
+                    _ => not_supported!("dyn unsizing from non pointers"),
+                },
+                _ => not_supported!("unknown unsized cast"),
+            },
+        })
+    }
+
     fn layout_of_variant(
         &mut self,
         x: VariantId,
@@ -921,7 +1118,7 @@ impl Evaluator<'_> {
                 if AdtId::from(f.parent) == adt {
                     // Computing the exact size of enums require resolving the enum discriminants. In order to prevent loops (and
                     // infinite sized type errors) we use a dummy layout
-                    let i = self.db.const_eval_discriminant(x)?;
+                    let i = self.const_eval_discriminant(x)?;
                     return Ok((16, self.layout(&TyBuilder::unit())?, Some((0, 16, i))));
                 }
             }
@@ -939,13 +1136,22 @@ impl Evaluator<'_> {
                     _ => not_supported!("multi variant layout for non-enums"),
                 };
                 let rustc_enum_variant_idx = RustcEnumVariantIdx(enum_variant_id.local_id);
-                let mut discriminant = self.db.const_eval_discriminant(enum_variant_id)?;
+                let mut discriminant = self.const_eval_discriminant(enum_variant_id)?;
                 let variant_layout = variants[rustc_enum_variant_idx].clone();
                 let have_tag = match tag_encoding {
                     TagEncoding::Direct => true,
                     TagEncoding::Niche { untagged_variant, niche_variants: _, niche_start } => {
-                        discriminant = discriminant.wrapping_add(niche_start as i128);
-                        untagged_variant != rustc_enum_variant_idx
+                        if untagged_variant == rustc_enum_variant_idx {
+                            false
+                        } else {
+                            discriminant = (variants
+                                .iter_enumerated()
+                                .filter(|(x, _)| *x != untagged_variant)
+                                .position(|(x, _)| x == rustc_enum_variant_idx)
+                                .unwrap() as i128)
+                                .wrapping_add(niche_start as i128);
+                            true
+                        }
                     }
                 };
                 (
@@ -970,7 +1176,7 @@ impl Evaluator<'_> {
         size: usize, // Not necessarily equal to variant_layout.size
         variant_layout: &Layout,
         tag: Option<(usize, usize, i128)>,
-        values: impl Iterator<Item = Interval>,
+        values: impl Iterator<Item = IntervalOrOwned>,
     ) -> Result<Vec<u8>> {
         let mut result = vec![0; size];
         if let Some((offset, size, value)) = tag {
@@ -987,6 +1193,10 @@ impl Evaluator<'_> {
     fn eval_operand(&mut self, x: &Operand, locals: &Locals<'_>) -> Result<Interval> {
         Ok(match x {
             Operand::Copy(p) | Operand::Move(p) => self.eval_place(p, locals)?,
+            Operand::Static(st) => {
+                let addr = self.eval_static(*st, locals)?;
+                Interval::new(addr, self.ptr_size())
+            }
             Operand::Constant(konst) => {
                 let data = &konst.data(Interner);
                 match &data.value {
@@ -1003,37 +1213,71 @@ impl Evaluator<'_> {
                         not_supported!("inference var constant")
                     }
                     chalk_ir::ConstValue::Placeholder(_) => not_supported!("placeholder constant"),
-                    chalk_ir::ConstValue::Concrete(c) => match &c.interned {
-                        ConstScalar::Bytes(v, memory_map) => {
-                            let mut v: Cow<'_, [u8]> = Cow::Borrowed(v);
-                            let patch_map = memory_map.transform_addresses(|b| {
-                                let addr = self.heap_allocate(b.len());
-                                self.write_memory(addr, b)?;
-                                Ok(addr.to_usize())
-                            })?;
-                            let size = self.size_of(&data.ty, locals)?.unwrap_or(v.len());
-                            if size != v.len() {
-                                // Handle self enum
-                                if size == 16 && v.len() < 16 {
-                                    v = Cow::Owned(pad16(&v, false).to_vec());
-                                } else if size < 16 && v.len() == 16 {
-                                    v = Cow::Owned(v[0..size].to_vec());
-                                } else {
-                                    return Err(MirEvalError::InvalidConst(konst.clone()));
-                                }
-                            }
-                            let addr = self.heap_allocate(size);
-                            self.write_memory(addr, &v)?;
-                            self.patch_addresses(&patch_map, addr, &data.ty, locals)?;
-                            Interval::new(addr, size)
-                        }
-                        ConstScalar::Unknown => not_supported!("evaluating unknown const"),
-                    },
+                    chalk_ir::ConstValue::Concrete(c) => {
+                        self.allocate_const_in_heap(c, &data.ty, locals, konst)?
+                    }
                 }
             }
         })
     }
 
+    fn allocate_const_in_heap(
+        &mut self,
+        c: &chalk_ir::ConcreteConst<Interner>,
+        ty: &Ty,
+        locals: &Locals<'_>,
+        konst: &chalk_ir::Const<Interner>,
+    ) -> Result<Interval> {
+        Ok(match &c.interned {
+            ConstScalar::Bytes(v, memory_map) => {
+                let mut v: Cow<'_, [u8]> = Cow::Borrowed(v);
+                let patch_map = memory_map.transform_addresses(|b| {
+                    let addr = self.heap_allocate(b.len(), 1); // FIXME: align is wrong
+                    self.write_memory(addr, b)?;
+                    Ok(addr.to_usize())
+                })?;
+                let (size, align) = self.size_align_of(ty, locals)?.unwrap_or((v.len(), 1));
+                if size != v.len() {
+                    // Handle self enum
+                    if size == 16 && v.len() < 16 {
+                        v = Cow::Owned(pad16(&v, false).to_vec());
+                    } else if size < 16 && v.len() == 16 {
+                        v = Cow::Owned(v[0..size].to_vec());
+                    } else {
+                        return Err(MirEvalError::InvalidConst(konst.clone()));
+                    }
+                }
+                let addr = self.heap_allocate(size, align);
+                self.write_memory(addr, &v)?;
+                self.patch_addresses(&patch_map, &memory_map.vtable, addr, ty, locals)?;
+                Interval::new(addr, size)
+            }
+            ConstScalar::UnevaluatedConst(const_id, subst) => {
+                let subst = self.subst_filler(subst, locals);
+                let (const_id, subst) = lookup_impl_const(
+                    self.db,
+                    self.db.trait_environment_for_body(locals.body.owner),
+                    *const_id,
+                    subst,
+                );
+                let c = self.db.const_eval(const_id.into(), subst).map_err(|e| {
+                    let const_data = self.db.const_data(const_id);
+                    MirEvalError::ConstEvalError(
+                        const_data.name.as_ref().and_then(|x| x.as_str()).unwrap_or("_").to_owned(),
+                        Box::new(e),
+                    )
+                })?;
+                if let chalk_ir::ConstValue::Concrete(c) = &c.data(Interner).value {
+                    if let ConstScalar::Bytes(_, _) = &c.interned {
+                        return self.allocate_const_in_heap(&c, ty, locals, konst);
+                    }
+                }
+                not_supported!("failing at evaluating unevaluated const");
+            }
+            ConstScalar::Unknown => not_supported!("evaluating unknown const"),
+        })
+    }
+
     fn eval_place(&mut self, p: &Place, locals: &Locals<'_>) -> Result<Interval> {
         let addr = self.place_addr(p, locals)?;
         Ok(Interval::new(
@@ -1046,53 +1290,61 @@ impl Evaluator<'_> {
         let (mem, pos) = match addr {
             Stack(x) => (&self.stack, x),
             Heap(x) => (&self.heap, x),
-            Invalid(_) => {
-                return Err(MirEvalError::UndefinedBehavior("read invalid memory address"))
+            Invalid(x) => {
+                return Err(MirEvalError::UndefinedBehavior(format!(
+                    "read invalid memory address {x} with size {size}"
+                )));
             }
         };
-        mem.get(pos..pos + size).ok_or(MirEvalError::UndefinedBehavior("out of bound memory read"))
+        mem.get(pos..pos + size)
+            .ok_or_else(|| MirEvalError::UndefinedBehavior("out of bound memory read".to_string()))
     }
 
     fn write_memory(&mut self, addr: Address, r: &[u8]) -> Result<()> {
         let (mem, pos) = match addr {
             Stack(x) => (&mut self.stack, x),
             Heap(x) => (&mut self.heap, x),
-            Invalid(_) => {
-                return Err(MirEvalError::UndefinedBehavior("write invalid memory address"))
+            Invalid(x) => {
+                return Err(MirEvalError::UndefinedBehavior(format!(
+                    "write invalid memory address {x} with content {r:?}"
+                )));
             }
         };
         mem.get_mut(pos..pos + r.len())
-            .ok_or(MirEvalError::UndefinedBehavior("out of bound memory write"))?
+            .ok_or_else(|| {
+                MirEvalError::UndefinedBehavior("out of bound memory write".to_string())
+            })?
             .copy_from_slice(r);
         Ok(())
     }
 
-    fn size_of(&self, ty: &Ty, locals: &Locals<'_>) -> Result<Option<usize>> {
+    fn size_align_of(&self, ty: &Ty, locals: &Locals<'_>) -> Result<Option<(usize, usize)>> {
         if let DefWithBodyId::VariantId(f) = locals.body.owner {
             if let Some((adt, _)) = ty.as_adt() {
                 if AdtId::from(f.parent) == adt {
                     // Computing the exact size of enums require resolving the enum discriminants. In order to prevent loops (and
                     // infinite sized type errors) we use a dummy size
-                    return Ok(Some(16));
+                    return Ok(Some((16, 16)));
                 }
             }
         }
-        let ty = &self.ty_filler(ty, locals.subst, locals.body.owner)?;
-        let layout = self.layout(ty);
+        let layout = self.layout_filled(ty, locals);
         if self.assert_placeholder_ty_is_unused {
             if matches!(layout, Err(MirEvalError::LayoutError(LayoutError::HasPlaceholder, _))) {
-                return Ok(Some(0));
+                return Ok(Some((0, 1)));
             }
         }
         let layout = layout?;
-        Ok(layout.is_sized().then(|| layout.size.bytes_usize()))
+        Ok(layout
+            .is_sized()
+            .then(|| (layout.size.bytes_usize(), layout.align.abi.bytes() as usize)))
     }
 
     /// A version of `self.size_of` which returns error if the type is unsized. `what` argument should
     /// be something that complete this: `error: type {ty} was unsized. {what} should be sized`
     fn size_of_sized(&self, ty: &Ty, locals: &Locals<'_>, what: &'static str) -> Result<usize> {
-        match self.size_of(ty, locals)? {
-            Some(x) => Ok(x),
+        match self.size_align_of(ty, locals)? {
+            Some(x) => Ok(x.0),
             None => Err(MirEvalError::TypeIsUnsized(ty.clone(), what)),
         }
     }
@@ -1120,7 +1372,7 @@ impl Evaluator<'_> {
         struct Filler<'a> {
             db: &'a dyn HirDatabase,
             subst: &'a Substitution,
-            skip_params: usize,
+            generics: Option<Generics>,
         }
         impl FallibleTypeFolder<Interner> for Filler<'_> {
             type Error = MirEvalError;
@@ -1144,7 +1396,11 @@ impl Evaluator<'_> {
                         match impl_trait_id {
                             crate::ImplTraitId::ReturnTypeImplTrait(func, idx) => {
                                 let infer = self.db.infer(func.into());
-                                let filler = &mut Filler { db: self.db, subst, skip_params: 0 };
+                                let filler = &mut Filler {
+                                    db: self.db,
+                                    subst,
+                                    generics: Some(generics(self.db.upcast(), func.into())),
+                                };
                                 filler.try_fold_ty(infer.type_of_rpit[idx].clone(), outer_binder)
                             }
                             crate::ImplTraitId::AsyncBlockTypeImplTrait(_, _) => {
@@ -1162,22 +1418,36 @@ impl Evaluator<'_> {
                 _outer_binder: DebruijnIndex,
             ) -> std::result::Result<Ty, Self::Error> {
                 let x = from_placeholder_idx(self.db, idx);
+                let Some(idx) = self.generics.as_ref().and_then(|g| g.param_idx(x)) else {
+                    not_supported!("missing idx in generics");
+                };
                 Ok(self
                     .subst
                     .as_slice(Interner)
-                    .get((u32::from(x.local_id.into_raw()) as usize) + self.skip_params)
+                    .get(idx)
                     .and_then(|x| x.ty(Interner))
-                    .ok_or(MirEvalError::TypeError("Generic arg not provided"))?
+                    .ok_or_else(|| MirEvalError::GenericArgNotProvided(x, self.subst.clone()))?
                     .clone())
             }
         }
-        let filler = &mut Filler { db: self.db, subst, skip_params: 0 };
-        Ok(normalize(self.db, owner, ty.clone().try_fold_with(filler, DebruijnIndex::INNERMOST)?))
+        let g_def = match owner {
+            DefWithBodyId::FunctionId(f) => Some(f.into()),
+            DefWithBodyId::StaticId(_) => None,
+            DefWithBodyId::ConstId(f) => Some(f.into()),
+            DefWithBodyId::VariantId(f) => Some(f.into()),
+        };
+        let generics = g_def.map(|g_def| generics(self.db.upcast(), g_def));
+        let filler = &mut Filler { db: self.db, subst, generics };
+        Ok(normalize(
+            self.db,
+            self.trait_env.clone(),
+            ty.clone().try_fold_with(filler, DebruijnIndex::INNERMOST)?,
+        ))
     }
 
-    fn heap_allocate(&mut self, s: usize) -> Address {
+    fn heap_allocate(&mut self, size: usize, _align: usize) -> Address {
         let pos = self.heap.len();
-        self.heap.extend(iter::repeat(0).take(s));
+        self.heap.extend(iter::repeat(0).take(size));
         Address::Heap(pos)
     }
 
@@ -1185,16 +1455,6 @@ impl Evaluator<'_> {
         self.interpret_mir(&body, vec![].into_iter(), Substitution::empty(Interner))
     }
 
-    fn detect_lang_function(&self, def: FunctionId) -> Option<LangItem> {
-        use LangItem::*;
-        let candidate = lang_attr(self.db.upcast(), def)?;
-        // We want to execute these functions with special logic
-        if [PanicFmt, BeginPanic, SliceLen].contains(&candidate) {
-            return Some(candidate);
-        }
-        None
-    }
-
     fn detect_fn_trait(&self, def: FunctionId) -> Option<FnTrait> {
         use LangItem::*;
         let ItemContainerId::TraitId(parent) = self.db.lookup_intern_function(def).container else {
@@ -1214,9 +1474,9 @@ impl Evaluator<'_> {
         let mut mm = MemoryMap::default();
         match ty.kind(Interner) {
             TyKind::Ref(_, _, t) => {
-                let size = self.size_of(t, locals)?;
+                let size = self.size_align_of(t, locals)?;
                 match size {
-                    Some(size) => {
+                    Some((size, _)) => {
                         let addr_usize = from_bytes!(usize, bytes);
                         mm.insert(
                             addr_usize,
@@ -1246,15 +1506,17 @@ impl Evaluator<'_> {
     fn patch_addresses(
         &mut self,
         patch_map: &HashMap<usize, usize>,
+        old_vtable: &VTableMap,
         addr: Address,
         ty: &Ty,
         locals: &Locals<'_>,
     ) -> Result<()> {
         // FIXME: support indirect references
+        let layout = self.layout(ty)?;
         let my_size = self.size_of_sized(ty, locals, "value to patch address")?;
         match ty.kind(Interner) {
             TyKind::Ref(_, _, t) => {
-                let size = self.size_of(t, locals)?;
+                let size = self.size_align_of(t, locals)?;
                 match size {
                     Some(_) => {
                         let current = from_bytes!(usize, self.read_memory(addr, my_size)?);
@@ -1270,98 +1532,50 @@ impl Evaluator<'_> {
                     }
                 }
             }
-            _ => (),
-        }
-        Ok(())
-    }
-
-    fn exec_intrinsic(
-        &mut self,
-        as_str: &str,
-        args: &[IntervalAndTy],
-        generic_args: Substitution,
-        destination: Interval,
-        locals: &Locals<'_>,
-    ) -> Result<()> {
-        match as_str {
-            "size_of" => {
-                let Some(ty) = generic_args.as_slice(Interner).get(0).and_then(|x| x.ty(Interner)) else {
-                    return Err(MirEvalError::TypeError("size_of generic arg is not provided"));
-                };
-                let size = self.size_of_sized(ty, locals, "size_of arg")?;
-                destination.write_from_bytes(self, &size.to_le_bytes()[0..destination.size])
-            }
-            "wrapping_add" => {
-                let [lhs, rhs] = args else {
-                    return Err(MirEvalError::TypeError("const_eval_select args are not provided"));
-                };
-                let lhs = u128::from_le_bytes(pad16(lhs.get(self)?, false));
-                let rhs = u128::from_le_bytes(pad16(rhs.get(self)?, false));
-                let ans = lhs.wrapping_add(rhs);
-                destination.write_from_bytes(self, &ans.to_le_bytes()[0..destination.size])
-            }
-            "copy" | "copy_nonoverlapping" => {
-                let [src, dst, offset] = args else {
-                    return Err(MirEvalError::TypeError("copy_nonoverlapping args are not provided"));
-                };
-                let Some(ty) = generic_args.as_slice(Interner).get(0).and_then(|x| x.ty(Interner)) else {
-                    return Err(MirEvalError::TypeError("copy_nonoverlapping generic arg is not provided"));
-                };
-                let src = Address::from_bytes(src.get(self)?)?;
-                let dst = Address::from_bytes(dst.get(self)?)?;
-                let offset = from_bytes!(usize, offset.get(self)?);
-                let size = self.size_of_sized(ty, locals, "copy_nonoverlapping ptr type")?;
-                let size = offset * size;
-                let src = Interval { addr: src, size };
-                let dst = Interval { addr: dst, size };
-                dst.write_from_interval(self, src)
-            }
-            "offset" | "arith_offset" => {
-                let [ptr, offset] = args else {
-                    return Err(MirEvalError::TypeError("offset args are not provided"));
-                };
-                let Some(ty) = generic_args.as_slice(Interner).get(0).and_then(|x| x.ty(Interner)) else {
-                    return Err(MirEvalError::TypeError("offset generic arg is not provided"));
-                };
-                let ptr = u128::from_le_bytes(pad16(ptr.get(self)?, false));
-                let offset = u128::from_le_bytes(pad16(offset.get(self)?, false));
-                let size = self.size_of_sized(ty, locals, "offset ptr type")? as u128;
-                let ans = ptr + offset * size;
-                destination.write_from_bytes(self, &ans.to_le_bytes()[0..destination.size])
-            }
-            "assert_inhabited" | "assert_zero_valid" | "assert_uninit_valid" => {
-                // FIXME: We should actually implement these checks
-                Ok(())
-            }
-            "forget" => {
-                // We don't call any drop glue yet, so there is nothing here
-                Ok(())
-            }
-            "transmute" => {
-                let [arg] = args else {
-                    return Err(MirEvalError::TypeError("trasmute arg is not provided"));
-                };
-                destination.write_from_interval(self, arg.interval)
+            TyKind::Function(_) => {
+                let ty = old_vtable.ty_of_bytes(self.read_memory(addr, my_size)?)?.clone();
+                let new_id = self.vtable_map.id(ty);
+                self.write_memory(addr, &new_id.to_le_bytes())?;
             }
-            "const_eval_select" => {
-                let [tuple, const_fn, _] = args else {
-                    return Err(MirEvalError::TypeError("const_eval_select args are not provided"));
-                };
-                let mut args = vec![const_fn.clone()];
-                let TyKind::Tuple(_, fields) = tuple.ty.kind(Interner) else {
-                    return Err(MirEvalError::TypeError("const_eval_select arg[0] is not a tuple"));
-                };
-                let layout = self.layout(&tuple.ty)?;
-                for (i, field) in fields.iter(Interner).enumerate() {
-                    let field = field.assert_ty_ref(Interner).clone();
-                    let offset = layout.fields.offset(i).bytes_usize();
-                    let addr = tuple.interval.addr.offset(offset);
-                    args.push(IntervalAndTy::new(addr, field, self, locals)?);
+            TyKind::Adt(id, subst) => match id.0 {
+                AdtId::StructId(s) => {
+                    for (i, (_, ty)) in self.db.field_types(s.into()).iter().enumerate() {
+                        let offset = layout.fields.offset(i).bytes_usize();
+                        let ty = ty.clone().substitute(Interner, subst);
+                        self.patch_addresses(
+                            patch_map,
+                            old_vtable,
+                            addr.offset(offset),
+                            &ty,
+                            locals,
+                        )?;
+                    }
                 }
-                self.exec_fn_trait(&args, destination, locals)
-            }
-            _ => not_supported!("unknown intrinsic {as_str}"),
+                AdtId::UnionId(_) => (),
+                AdtId::EnumId(_) => (),
+            },
+            TyKind::AssociatedType(_, _)
+            | TyKind::Scalar(_)
+            | TyKind::Tuple(_, _)
+            | TyKind::Array(_, _)
+            | TyKind::Slice(_)
+            | TyKind::Raw(_, _)
+            | TyKind::OpaqueType(_, _)
+            | TyKind::FnDef(_, _)
+            | TyKind::Str
+            | TyKind::Never
+            | TyKind::Closure(_, _)
+            | TyKind::Generator(_, _)
+            | TyKind::GeneratorWitness(_, _)
+            | TyKind::Foreign(_)
+            | TyKind::Error
+            | TyKind::Placeholder(_)
+            | TyKind::Dyn(_)
+            | TyKind::Alias(_)
+            | TyKind::BoundVar(_)
+            | TyKind::InferenceVar(_, _) => (),
         }
+        Ok(())
     }
 
     fn exec_fn_pointer(
@@ -1370,13 +1584,18 @@ impl Evaluator<'_> {
         destination: Interval,
         args: &[IntervalAndTy],
         locals: &Locals<'_>,
+        span: MirSpan,
     ) -> Result<()> {
         let id = from_bytes!(usize, bytes.get(self)?);
         let next_ty = self.vtable_map.ty(id)?.clone();
-        if let TyKind::FnDef(def, generic_args) = &next_ty.data(Interner).kind {
-            self.exec_fn_def(*def, generic_args, destination, args, &locals)?;
-        } else {
-            return Err(MirEvalError::TypeError("function pointer to non function"));
+        match &next_ty.data(Interner).kind {
+            TyKind::FnDef(def, generic_args) => {
+                self.exec_fn_def(*def, generic_args, destination, args, &locals, span)?;
+            }
+            TyKind::Closure(id, subst) => {
+                self.exec_closure(*id, bytes.slice(0..0), subst, destination, args, locals, span)?;
+            }
+            _ => return Err(MirEvalError::TypeError("function pointer to non function")),
         }
         Ok(())
     }
@@ -1388,6 +1607,8 @@ impl Evaluator<'_> {
         generic_args: &Substitution,
         destination: Interval,
         args: &[IntervalAndTy],
+        locals: &Locals<'_>,
+        span: MirSpan,
     ) -> Result<()> {
         let mir_body = self
             .db
@@ -1396,7 +1617,16 @@ impl Evaluator<'_> {
         let arg_bytes = iter::once(Ok(closure_data.get(self)?.to_owned()))
             .chain(args.iter().map(|x| Ok(x.get(&self)?.to_owned())))
             .collect::<Result<Vec<_>>>()?;
-        let bytes = self.interpret_mir(&mir_body, arg_bytes.into_iter(), generic_args.clone())?;
+        let bytes = self
+            .interpret_mir(&mir_body, arg_bytes.into_iter(), generic_args.clone())
+            .map_err(|e| {
+                MirEvalError::InFunction(
+                    Either::Right(closure),
+                    Box::new(e),
+                    span,
+                    locals.body.owner,
+                )
+            })?;
         destination.write_from_bytes(self, &bytes)
     }
 
@@ -1407,16 +1637,17 @@ impl Evaluator<'_> {
         destination: Interval,
         args: &[IntervalAndTy],
         locals: &Locals<'_>,
+        span: MirSpan,
     ) -> Result<()> {
         let def: CallableDefId = from_chalk(self.db, def);
         let generic_args = self.subst_filler(generic_args, &locals);
         match def {
             CallableDefId::FunctionId(def) => {
                 if let Some(_) = self.detect_fn_trait(def) {
-                    self.exec_fn_trait(&args, destination, locals)?;
+                    self.exec_fn_trait(&args, destination, locals, span)?;
                     return Ok(());
                 }
-                self.exec_fn_with_args(def, args, generic_args, locals, destination)?;
+                self.exec_fn_with_args(def, args, generic_args, locals, destination, span)?;
             }
             CallableDefId::StructId(id) => {
                 let (size, variant_layout, tag) =
@@ -1425,7 +1656,7 @@ impl Evaluator<'_> {
                     size,
                     &variant_layout,
                     tag,
-                    args.iter().map(|x| x.interval),
+                    args.iter().map(|x| x.interval.into()),
                 )?;
                 destination.write_from_bytes(self, &result)?;
             }
@@ -1436,7 +1667,7 @@ impl Evaluator<'_> {
                     size,
                     &variant_layout,
                     tag,
-                    args.iter().map(|x| x.interval),
+                    args.iter().map(|x| x.interval.into()),
                 )?;
                 destination.write_from_bytes(self, &result)?;
             }
@@ -1451,50 +1682,37 @@ impl Evaluator<'_> {
         generic_args: Substitution,
         locals: &Locals<'_>,
         destination: Interval,
+        span: MirSpan,
     ) -> Result<()> {
-        let function_data = self.db.function_data(def);
-        let is_intrinsic = match &function_data.abi {
-            Some(abi) => *abi == Interned::new_str("rust-intrinsic"),
-            None => match def.lookup(self.db.upcast()).container {
-                hir_def::ItemContainerId::ExternBlockId(block) => {
-                    let id = block.lookup(self.db.upcast()).id;
-                    id.item_tree(self.db.upcast())[id.value].abi.as_deref()
-                        == Some("rust-intrinsic")
-                }
-                _ => false,
-            },
-        };
-        if is_intrinsic {
-            return self.exec_intrinsic(
-                function_data.name.as_text().unwrap_or_default().as_str(),
-                args,
-                generic_args,
-                destination,
-                &locals,
-            );
+        if self.detect_and_exec_special_function(
+            def,
+            args,
+            &generic_args,
+            locals,
+            destination,
+            span,
+        )? {
+            return Ok(());
         }
         let arg_bytes =
             args.iter().map(|x| Ok(x.get(&self)?.to_owned())).collect::<Result<Vec<_>>>()?;
-        let result = if let Some(x) = self.detect_lang_function(def) {
-            self.exec_lang_item(x, &arg_bytes)?
-        } else {
-            if let Some(self_ty_idx) =
-                is_dyn_method(self.db, self.trait_env.clone(), def, generic_args.clone())
-            {
-                // In the layout of current possible receiver, which at the moment of writing this code is one of
-                // `&T`, `&mut T`, `Box<T>`, `Rc<T>`, `Arc<T>`, and `Pin<P>` where `P` is one of possible receivers,
-                // the vtable is exactly in the `[ptr_size..2*ptr_size]` bytes. So we can use it without branching on
-                // the type.
-                let ty = self
-                    .vtable_map
-                    .ty_of_bytes(&arg_bytes[0][self.ptr_size()..self.ptr_size() * 2])?;
-                let mut args_for_target = args.to_vec();
-                args_for_target[0] = IntervalAndTy {
-                    interval: args_for_target[0].interval.slice(0..self.ptr_size()),
-                    ty: ty.clone(),
-                };
-                let ty = GenericArgData::Ty(ty.clone()).intern(Interner);
-                let generics_for_target = Substitution::from_iter(
+        if let Some(self_ty_idx) =
+            is_dyn_method(self.db, self.trait_env.clone(), def, generic_args.clone())
+        {
+            // In the layout of current possible receiver, which at the moment of writing this code is one of
+            // `&T`, `&mut T`, `Box<T>`, `Rc<T>`, `Arc<T>`, and `Pin<P>` where `P` is one of possible recievers,
+            // the vtable is exactly in the `[ptr_size..2*ptr_size]` bytes. So we can use it without branching on
+            // the type.
+            let ty =
+                self.vtable_map.ty_of_bytes(&arg_bytes[0][self.ptr_size()..self.ptr_size() * 2])?;
+            let mut args_for_target = args.to_vec();
+            args_for_target[0] = IntervalAndTy {
+                interval: args_for_target[0].interval.slice(0..self.ptr_size()),
+                ty: ty.clone(),
+            };
+            let ty = GenericArgData::Ty(ty.clone()).intern(Interner);
+            let generics_for_target =
+                Substitution::from_iter(
                     Interner,
                     generic_args.iter(Interner).enumerate().map(|(i, x)| {
                         if i == self_ty_idx {
@@ -1504,23 +1722,25 @@ impl Evaluator<'_> {
                         }
                     }),
                 );
-                return self.exec_fn_with_args(
-                    def,
-                    &args_for_target,
-                    generics_for_target,
-                    locals,
-                    destination,
-                );
-            }
-            let (imp, generic_args) =
-                lookup_impl_method(self.db, self.trait_env.clone(), def, generic_args);
-            let generic_args = self.subst_filler(&generic_args, &locals);
-            let def = imp.into();
-            let mir_body =
-                self.db.mir_body(def).map_err(|e| MirEvalError::MirLowerError(imp, e))?;
-            self.interpret_mir(&mir_body, arg_bytes.iter().cloned(), generic_args)
-                .map_err(|e| MirEvalError::InFunction(imp, Box::new(e)))?
-        };
+            return self.exec_fn_with_args(
+                def,
+                &args_for_target,
+                generics_for_target,
+                locals,
+                destination,
+                span,
+            );
+        }
+        let (imp, generic_args) =
+            lookup_impl_method(self.db, self.trait_env.clone(), def, generic_args);
+        let generic_args = self.subst_filler(&generic_args, &locals);
+        let def = imp.into();
+        let mir_body = self.db.mir_body(def).map_err(|e| MirEvalError::MirLowerError(imp, e))?;
+        let result = self
+            .interpret_mir(&mir_body, arg_bytes.iter().cloned(), generic_args)
+            .map_err(|e| {
+                MirEvalError::InFunction(Either::Left(imp), Box::new(e), span, locals.body.owner)
+            })?;
         destination.write_from_bytes(self, &result)?;
         Ok(())
     }
@@ -1530,6 +1750,7 @@ impl Evaluator<'_> {
         args: &[IntervalAndTy],
         destination: Interval,
         locals: &Locals<'_>,
+        span: MirSpan,
     ) -> Result<()> {
         let func = args.get(0).ok_or(MirEvalError::TypeError("fn trait with no arg"))?;
         let mut func_ty = func.ty.clone();
@@ -1547,35 +1768,69 @@ impl Evaluator<'_> {
         }
         match &func_ty.data(Interner).kind {
             TyKind::FnDef(def, subst) => {
-                self.exec_fn_def(*def, subst, destination, &args[1..], locals)?;
+                self.exec_fn_def(*def, subst, destination, &args[1..], locals, span)?;
             }
             TyKind::Function(_) => {
-                self.exec_fn_pointer(func_data, destination, &args[1..], locals)?;
+                self.exec_fn_pointer(func_data, destination, &args[1..], locals, span)?;
             }
             TyKind::Closure(closure, subst) => {
-                self.exec_closure(*closure, func_data, subst, destination, &args[1..])?;
+                self.exec_closure(
+                    *closure,
+                    func_data,
+                    &Substitution::from_iter(Interner, ClosureSubst(subst).parent_subst()),
+                    destination,
+                    &args[1..],
+                    locals,
+                    span,
+                )?;
             }
             x => not_supported!("Call FnTrait methods with type {x:?}"),
         }
         Ok(())
     }
 
-    fn exec_lang_item(&self, x: LangItem, args: &[Vec<u8>]) -> Result<Vec<u8>> {
-        use LangItem::*;
-        let mut args = args.iter();
-        match x {
-            // FIXME: we want to find the panic message from arguments, but it wouldn't work
-            // currently even if we do that, since macro expansion of panic related macros
-            // is dummy.
-            PanicFmt | BeginPanic => Err(MirEvalError::Panic("<format-args>".to_string())),
-            SliceLen => {
-                let arg = args
-                    .next()
-                    .ok_or(MirEvalError::TypeError("argument of <[T]>::len() is not provided"))?;
-                let ptr_size = arg.len() / 2;
-                Ok(arg[ptr_size..].into())
+    fn eval_static(&mut self, st: StaticId, locals: &Locals<'_>) -> Result<Address> {
+        if let Some(o) = self.static_locations.get(&st) {
+            return Ok(*o);
+        };
+        let static_data = self.db.static_data(st);
+        let result = if !static_data.is_extern {
+            let konst =
+                self.db.const_eval(st.into(), Substitution::empty(Interner)).map_err(|e| {
+                    MirEvalError::ConstEvalError(
+                        static_data.name.as_str().unwrap_or("_").to_owned(),
+                        Box::new(e),
+                    )
+                })?;
+            let data = &konst.data(Interner);
+            if let chalk_ir::ConstValue::Concrete(c) = &data.value {
+                self.allocate_const_in_heap(&c, &data.ty, locals, &konst)?
+            } else {
+                not_supported!("unevaluatable static");
+            }
+        } else {
+            let ty = &self.db.infer(st.into())[self.db.body(st.into()).body_expr];
+            let Some((size, align)) = self.size_align_of(&ty, locals)? else {
+                not_supported!("unsized extern static");
+            };
+            let addr = self.heap_allocate(size, align);
+            Interval::new(addr, size)
+        };
+        let addr = self.heap_allocate(self.ptr_size(), self.ptr_size());
+        self.write_memory(addr, &result.addr.to_bytes())?;
+        self.static_locations.insert(st, addr);
+        Ok(addr)
+    }
+
+    fn const_eval_discriminant(&self, variant: EnumVariantId) -> Result<i128> {
+        let r = self.db.const_eval_discriminant(variant);
+        match r {
+            Ok(r) => Ok(r),
+            Err(e) => {
+                let data = self.db.enum_data(variant.parent);
+                let name = format!("{}::{}", data.name, data.variants[variant.local_id].name);
+                Err(MirEvalError::ConstEvalError(name, Box::new(e)))
             }
-            x => not_supported!("Executing lang item {x:?}"),
         }
     }
 }
diff --git a/crates/hir-ty/src/mir/eval/shim.rs b/crates/hir-ty/src/mir/eval/shim.rs
new file mode 100644
index 00000000000..78938af15b8
--- /dev/null
+++ b/crates/hir-ty/src/mir/eval/shim.rs
@@ -0,0 +1,396 @@
+//! Interpret intrinsics, lang items and `extern "C"` wellknown functions which their implementation
+//! is not available.
+
+use super::*;
+
+macro_rules! from_bytes {
+    ($ty:tt, $value:expr) => {
+        ($ty::from_le_bytes(match ($value).try_into() {
+            Ok(x) => x,
+            Err(_) => return Err(MirEvalError::TypeError("mismatched size")),
+        }))
+    };
+}
+
+macro_rules! not_supported {
+    ($x: expr) => {
+        return Err(MirEvalError::NotSupported(format!($x)))
+    };
+}
+
+impl Evaluator<'_> {
+    pub(super) fn detect_and_exec_special_function(
+        &mut self,
+        def: FunctionId,
+        args: &[IntervalAndTy],
+        generic_args: &Substitution,
+        locals: &Locals<'_>,
+        destination: Interval,
+        span: MirSpan,
+    ) -> Result<bool> {
+        let function_data = self.db.function_data(def);
+        let is_intrinsic = match &function_data.abi {
+            Some(abi) => *abi == Interned::new_str("rust-intrinsic"),
+            None => match def.lookup(self.db.upcast()).container {
+                hir_def::ItemContainerId::ExternBlockId(block) => {
+                    let id = block.lookup(self.db.upcast()).id;
+                    id.item_tree(self.db.upcast())[id.value].abi.as_deref()
+                        == Some("rust-intrinsic")
+                }
+                _ => false,
+            },
+        };
+        if is_intrinsic {
+            self.exec_intrinsic(
+                function_data.name.as_text().unwrap_or_default().as_str(),
+                args,
+                generic_args,
+                destination,
+                &locals,
+                span,
+            )?;
+            return Ok(true);
+        }
+        let alloc_fn = function_data
+            .attrs
+            .iter()
+            .filter_map(|x| x.path().as_ident())
+            .filter_map(|x| x.as_str())
+            .find(|x| {
+                [
+                    "rustc_allocator",
+                    "rustc_deallocator",
+                    "rustc_reallocator",
+                    "rustc_allocator_zeroed",
+                ]
+                .contains(x)
+            });
+        if let Some(alloc_fn) = alloc_fn {
+            self.exec_alloc_fn(alloc_fn, args, destination)?;
+            return Ok(true);
+        }
+        if let Some(x) = self.detect_lang_function(def) {
+            let arg_bytes =
+                args.iter().map(|x| Ok(x.get(&self)?.to_owned())).collect::<Result<Vec<_>>>()?;
+            let result = self.exec_lang_item(x, &arg_bytes)?;
+            destination.write_from_bytes(self, &result)?;
+            return Ok(true);
+        }
+        Ok(false)
+    }
+
+    fn exec_alloc_fn(
+        &mut self,
+        alloc_fn: &str,
+        args: &[IntervalAndTy],
+        destination: Interval,
+    ) -> Result<()> {
+        match alloc_fn {
+            "rustc_allocator_zeroed" | "rustc_allocator" => {
+                let [size, align] = args else {
+                    return Err(MirEvalError::TypeError("rustc_allocator args are not provided"));
+                };
+                let size = from_bytes!(usize, size.get(self)?);
+                let align = from_bytes!(usize, align.get(self)?);
+                let result = self.heap_allocate(size, align);
+                destination.write_from_bytes(self, &result.to_bytes())?;
+            }
+            "rustc_deallocator" => { /* no-op for now */ }
+            "rustc_reallocator" => {
+                let [ptr, old_size, align, new_size] = args else {
+                    return Err(MirEvalError::TypeError("rustc_allocator args are not provided"));
+                };
+                let ptr = Address::from_bytes(ptr.get(self)?)?;
+                let old_size = from_bytes!(usize, old_size.get(self)?);
+                let new_size = from_bytes!(usize, new_size.get(self)?);
+                let align = from_bytes!(usize, align.get(self)?);
+                let result = self.heap_allocate(new_size, align);
+                Interval { addr: result, size: old_size }
+                    .write_from_interval(self, Interval { addr: ptr, size: old_size })?;
+                destination.write_from_bytes(self, &result.to_bytes())?;
+            }
+            _ => not_supported!("unknown alloc function"),
+        }
+        Ok(())
+    }
+
+    fn detect_lang_function(&self, def: FunctionId) -> Option<LangItem> {
+        use LangItem::*;
+        let candidate = lang_attr(self.db.upcast(), def)?;
+        // We want to execute these functions with special logic
+        if [PanicFmt, BeginPanic, SliceLen].contains(&candidate) {
+            return Some(candidate);
+        }
+        None
+    }
+
+    fn exec_lang_item(&self, x: LangItem, args: &[Vec<u8>]) -> Result<Vec<u8>> {
+        use LangItem::*;
+        let mut args = args.iter();
+        match x {
+            // FIXME: we want to find the panic message from arguments, but it wouldn't work
+            // currently even if we do that, since macro expansion of panic related macros
+            // is dummy.
+            PanicFmt | BeginPanic => Err(MirEvalError::Panic("<format-args>".to_string())),
+            SliceLen => {
+                let arg = args
+                    .next()
+                    .ok_or(MirEvalError::TypeError("argument of <[T]>::len() is not provided"))?;
+                let ptr_size = arg.len() / 2;
+                Ok(arg[ptr_size..].into())
+            }
+            x => not_supported!("Executing lang item {x:?}"),
+        }
+    }
+
+    fn exec_intrinsic(
+        &mut self,
+        as_str: &str,
+        args: &[IntervalAndTy],
+        generic_args: &Substitution,
+        destination: Interval,
+        locals: &Locals<'_>,
+        span: MirSpan,
+    ) -> Result<()> {
+        // We are a single threaded runtime with no UB checking and no optimization, so
+        // we can implement these as normal functions.
+        if let Some(name) = as_str.strip_prefix("atomic_") {
+            let Some(ty) = generic_args.as_slice(Interner).get(0).and_then(|x| x.ty(Interner)) else {
+                return Err(MirEvalError::TypeError("atomic intrinsic generic arg is not provided"));
+            };
+            let Some(arg0) = args.get(0) else {
+                return Err(MirEvalError::TypeError("atomic intrinsic arg0 is not provided"));
+            };
+            let arg0_addr = Address::from_bytes(arg0.get(self)?)?;
+            let arg0_interval = Interval::new(
+                arg0_addr,
+                self.size_of_sized(ty, locals, "atomic intrinsic type arg")?,
+            );
+            if name.starts_with("load_") {
+                return destination.write_from_interval(self, arg0_interval);
+            }
+            let Some(arg1) = args.get(1) else {
+                return Err(MirEvalError::TypeError("atomic intrinsic arg1 is not provided"));
+            };
+            if name.starts_with("store_") {
+                return arg0_interval.write_from_interval(self, arg1.interval);
+            }
+            if name.starts_with("xchg_") {
+                destination.write_from_interval(self, arg0_interval)?;
+                return arg0_interval.write_from_interval(self, arg1.interval);
+            }
+            if name.starts_with("xadd_") {
+                destination.write_from_interval(self, arg0_interval)?;
+                let lhs = u128::from_le_bytes(pad16(arg0_interval.get(self)?, false));
+                let rhs = u128::from_le_bytes(pad16(arg1.get(self)?, false));
+                let ans = lhs.wrapping_add(rhs);
+                return arg0_interval
+                    .write_from_bytes(self, &ans.to_le_bytes()[0..destination.size]);
+            }
+            if name.starts_with("xsub_") {
+                destination.write_from_interval(self, arg0_interval)?;
+                let lhs = u128::from_le_bytes(pad16(arg0_interval.get(self)?, false));
+                let rhs = u128::from_le_bytes(pad16(arg1.get(self)?, false));
+                let ans = lhs.wrapping_sub(rhs);
+                return arg0_interval
+                    .write_from_bytes(self, &ans.to_le_bytes()[0..destination.size]);
+            }
+            if name.starts_with("and_") {
+                destination.write_from_interval(self, arg0_interval)?;
+                let lhs = u128::from_le_bytes(pad16(arg0_interval.get(self)?, false));
+                let rhs = u128::from_le_bytes(pad16(arg1.get(self)?, false));
+                let ans = lhs & rhs;
+                return arg0_interval
+                    .write_from_bytes(self, &ans.to_le_bytes()[0..destination.size]);
+            }
+            if name.starts_with("or_") {
+                destination.write_from_interval(self, arg0_interval)?;
+                let lhs = u128::from_le_bytes(pad16(arg0_interval.get(self)?, false));
+                let rhs = u128::from_le_bytes(pad16(arg1.get(self)?, false));
+                let ans = lhs | rhs;
+                return arg0_interval
+                    .write_from_bytes(self, &ans.to_le_bytes()[0..destination.size]);
+            }
+            if name.starts_with("xor_") {
+                destination.write_from_interval(self, arg0_interval)?;
+                let lhs = u128::from_le_bytes(pad16(arg0_interval.get(self)?, false));
+                let rhs = u128::from_le_bytes(pad16(arg1.get(self)?, false));
+                let ans = lhs ^ rhs;
+                return arg0_interval
+                    .write_from_bytes(self, &ans.to_le_bytes()[0..destination.size]);
+            }
+            if name.starts_with("nand_") {
+                destination.write_from_interval(self, arg0_interval)?;
+                let lhs = u128::from_le_bytes(pad16(arg0_interval.get(self)?, false));
+                let rhs = u128::from_le_bytes(pad16(arg1.get(self)?, false));
+                let ans = !(lhs & rhs);
+                return arg0_interval
+                    .write_from_bytes(self, &ans.to_le_bytes()[0..destination.size]);
+            }
+            let Some(arg2) = args.get(2) else {
+                return Err(MirEvalError::TypeError("atomic intrinsic arg2 is not provided"));
+            };
+            if name.starts_with("cxchg_") || name.starts_with("cxchgweak_") {
+                let dest = if arg1.get(self)? == arg0_interval.get(self)? {
+                    arg0_interval.write_from_interval(self, arg2.interval)?;
+                    (arg1.interval, true)
+                } else {
+                    (arg0_interval, false)
+                };
+                let result_ty = TyKind::Tuple(
+                    2,
+                    Substitution::from_iter(Interner, [ty.clone(), TyBuilder::bool()]),
+                )
+                .intern(Interner);
+                let layout = self.layout(&result_ty)?;
+                let result = self.make_by_layout(
+                    layout.size.bytes_usize(),
+                    &layout,
+                    None,
+                    [
+                        IntervalOrOwned::Borrowed(dest.0),
+                        IntervalOrOwned::Owned(vec![u8::from(dest.1)]),
+                    ]
+                    .into_iter(),
+                )?;
+                return destination.write_from_bytes(self, &result);
+            }
+            not_supported!("unknown atomic intrinsic {name}");
+        }
+        match as_str {
+            "size_of" => {
+                let Some(ty) = generic_args.as_slice(Interner).get(0).and_then(|x| x.ty(Interner)) else {
+                    return Err(MirEvalError::TypeError("size_of generic arg is not provided"));
+                };
+                let size = self.size_of_sized(ty, locals, "size_of arg")?;
+                destination.write_from_bytes(self, &size.to_le_bytes()[0..destination.size])
+            }
+            "min_align_of" | "pref_align_of" => {
+                let Some(ty) = generic_args.as_slice(Interner).get(0).and_then(|x| x.ty(Interner)) else {
+                    return Err(MirEvalError::TypeError("align_of generic arg is not provided"));
+                };
+                let align = self.layout_filled(ty, locals)?.align.abi.bytes();
+                destination.write_from_bytes(self, &align.to_le_bytes()[0..destination.size])
+            }
+            "needs_drop" => {
+                let Some(ty) = generic_args.as_slice(Interner).get(0).and_then(|x| x.ty(Interner)) else {
+                    return Err(MirEvalError::TypeError("size_of generic arg is not provided"));
+                };
+                let result = !ty.clone().is_copy(self.db, locals.body.owner);
+                destination.write_from_bytes(self, &[u8::from(result)])
+            }
+            "ptr_guaranteed_cmp" => {
+                // FIXME: this is wrong for const eval, it should return 2 in some
+                // cases.
+                let [lhs, rhs] = args else {
+                    return Err(MirEvalError::TypeError("wrapping_add args are not provided"));
+                };
+                let ans = lhs.get(self)? == rhs.get(self)?;
+                destination.write_from_bytes(self, &[u8::from(ans)])
+            }
+            "wrapping_add" => {
+                let [lhs, rhs] = args else {
+                    return Err(MirEvalError::TypeError("wrapping_add args are not provided"));
+                };
+                let lhs = u128::from_le_bytes(pad16(lhs.get(self)?, false));
+                let rhs = u128::from_le_bytes(pad16(rhs.get(self)?, false));
+                let ans = lhs.wrapping_add(rhs);
+                destination.write_from_bytes(self, &ans.to_le_bytes()[0..destination.size])
+            }
+            "add_with_overflow" => {
+                let [lhs, rhs] = args else {
+                    return Err(MirEvalError::TypeError("const_eval_select args are not provided"));
+                };
+                let result_ty = TyKind::Tuple(
+                    2,
+                    Substitution::from_iter(Interner, [lhs.ty.clone(), TyBuilder::bool()]),
+                )
+                .intern(Interner);
+                let op_size =
+                    self.size_of_sized(&lhs.ty, locals, "operand of add_with_overflow")?;
+                let lhs = u128::from_le_bytes(pad16(lhs.get(self)?, false));
+                let rhs = u128::from_le_bytes(pad16(rhs.get(self)?, false));
+                let ans = lhs.wrapping_add(rhs);
+                let is_overflow = false;
+                let is_overflow = vec![u8::from(is_overflow)];
+                let layout = self.layout(&result_ty)?;
+                let result = self.make_by_layout(
+                    layout.size.bytes_usize(),
+                    &layout,
+                    None,
+                    [ans.to_le_bytes()[0..op_size].to_vec(), is_overflow]
+                        .into_iter()
+                        .map(IntervalOrOwned::Owned),
+                )?;
+                destination.write_from_bytes(self, &result)
+            }
+            "copy" | "copy_nonoverlapping" => {
+                let [src, dst, offset] = args else {
+                    return Err(MirEvalError::TypeError("copy_nonoverlapping args are not provided"));
+                };
+                let Some(ty) = generic_args.as_slice(Interner).get(0).and_then(|x| x.ty(Interner)) else {
+                    return Err(MirEvalError::TypeError("copy_nonoverlapping generic arg is not provided"));
+                };
+                let src = Address::from_bytes(src.get(self)?)?;
+                let dst = Address::from_bytes(dst.get(self)?)?;
+                let offset = from_bytes!(usize, offset.get(self)?);
+                let size = self.size_of_sized(ty, locals, "copy_nonoverlapping ptr type")?;
+                let size = offset * size;
+                let src = Interval { addr: src, size };
+                let dst = Interval { addr: dst, size };
+                dst.write_from_interval(self, src)
+            }
+            "offset" | "arith_offset" => {
+                let [ptr, offset] = args else {
+                    return Err(MirEvalError::TypeError("offset args are not provided"));
+                };
+                let Some(ty) = generic_args.as_slice(Interner).get(0).and_then(|x| x.ty(Interner)) else {
+                    return Err(MirEvalError::TypeError("offset generic arg is not provided"));
+                };
+                let ptr = u128::from_le_bytes(pad16(ptr.get(self)?, false));
+                let offset = u128::from_le_bytes(pad16(offset.get(self)?, false));
+                let size = self.size_of_sized(ty, locals, "offset ptr type")? as u128;
+                let ans = ptr + offset * size;
+                destination.write_from_bytes(self, &ans.to_le_bytes()[0..destination.size])
+            }
+            "assert_inhabited" | "assert_zero_valid" | "assert_uninit_valid" | "assume" => {
+                // FIXME: We should actually implement these checks
+                Ok(())
+            }
+            "forget" => {
+                // We don't call any drop glue yet, so there is nothing here
+                Ok(())
+            }
+            "transmute" => {
+                let [arg] = args else {
+                    return Err(MirEvalError::TypeError("trasmute arg is not provided"));
+                };
+                destination.write_from_interval(self, arg.interval)
+            }
+            "likely" | "unlikely" => {
+                let [arg] = args else {
+                    return Err(MirEvalError::TypeError("likely arg is not provided"));
+                };
+                destination.write_from_interval(self, arg.interval)
+            }
+            "const_eval_select" => {
+                let [tuple, const_fn, _] = args else {
+                    return Err(MirEvalError::TypeError("const_eval_select args are not provided"));
+                };
+                let mut args = vec![const_fn.clone()];
+                let TyKind::Tuple(_, fields) = tuple.ty.kind(Interner) else {
+                    return Err(MirEvalError::TypeError("const_eval_select arg[0] is not a tuple"));
+                };
+                let layout = self.layout(&tuple.ty)?;
+                for (i, field) in fields.iter(Interner).enumerate() {
+                    let field = field.assert_ty_ref(Interner).clone();
+                    let offset = layout.fields.offset(i).bytes_usize();
+                    let addr = tuple.interval.addr.offset(offset);
+                    args.push(IntervalAndTy::new(addr, field, self, locals)?);
+                }
+                self.exec_fn_trait(&args, destination, locals, span)
+            }
+            _ => not_supported!("unknown intrinsic {as_str}"),
+        }
+    }
+}
diff --git a/crates/hir-ty/src/mir/lower.rs b/crates/hir-ty/src/mir/lower.rs
index 37b27b39834..733f58e8f6b 100644
--- a/crates/hir-ty/src/mir/lower.rs
+++ b/crates/hir-ty/src/mir/lower.rs
@@ -1,14 +1,15 @@
 //! This module generates a polymorphic MIR from a hir body
 
-use std::{iter, mem, sync::Arc};
+use std::{fmt::Write, iter, mem, sync::Arc};
 
+use base_db::FileId;
 use chalk_ir::{BoundVar, ConstData, DebruijnIndex, TyKind};
 use hir_def::{
     body::Body,
     data::adt::{StructKind, VariantData},
     hir::{
-        Array, BindingAnnotation, BindingId, ExprId, LabelId, Literal, MatchArm, Pat, PatId,
-        RecordFieldPat, RecordLitField,
+        ArithOp, Array, BinaryOp, BindingAnnotation, BindingId, ExprId, LabelId, Literal, MatchArm,
+        Pat, PatId, RecordFieldPat, RecordLitField,
     },
     lang_item::{LangItem, LangItemTarget},
     path::Path,
@@ -18,6 +19,7 @@ use hir_def::{
 use hir_expand::name::Name;
 use la_arena::ArenaMap;
 use rustc_hash::FxHashMap;
+use syntax::TextRange;
 
 use crate::{
     consteval::ConstEvalError,
@@ -27,8 +29,9 @@ use crate::{
     inhabitedness::is_ty_uninhabited_from,
     layout::{layout_of_ty, LayoutError},
     mapping::ToChalk,
+    method_resolution::lookup_impl_const,
     static_lifetime,
-    utils::generics,
+    utils::{generics, ClosureSubst},
     Adjust, Adjustment, AutoBorrow, CallableDefId, TyBuilder, TyExt,
 };
 
@@ -62,14 +65,14 @@ struct MirLowerCtx<'a> {
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum MirLowerError {
-    ConstEvalError(Box<ConstEvalError>),
+    ConstEvalError(String, Box<ConstEvalError>),
     LayoutError(LayoutError),
     IncompleteExpr,
     /// Trying to lower a trait function, instead of an implementation
     TraitFunctionDefinition(TraitId, Name),
     UnresolvedName(String),
     RecordLiteralWithoutPath,
-    UnresolvedMethod,
+    UnresolvedMethod(String),
     UnresolvedField,
     MissingFunctionDefinition,
     TypeMismatch(TypeMismatch),
@@ -88,6 +91,46 @@ pub enum MirLowerError {
     UnaccessableLocal,
 }
 
+impl MirLowerError {
+    pub fn pretty_print(
+        &self,
+        f: &mut String,
+        db: &dyn HirDatabase,
+        span_formatter: impl Fn(FileId, TextRange) -> String,
+    ) -> std::result::Result<(), std::fmt::Error> {
+        match self {
+            MirLowerError::ConstEvalError(name, e) => {
+                writeln!(f, "In evaluating constant {name}")?;
+                match &**e {
+                    ConstEvalError::MirLowerError(e) => e.pretty_print(f, db, span_formatter)?,
+                    ConstEvalError::MirEvalError(e) => e.pretty_print(f, db, span_formatter)?,
+                }
+            }
+            MirLowerError::LayoutError(_)
+            | MirLowerError::IncompleteExpr
+            | MirLowerError::UnaccessableLocal
+            | MirLowerError::TraitFunctionDefinition(_, _)
+            | MirLowerError::UnresolvedName(_)
+            | MirLowerError::RecordLiteralWithoutPath
+            | MirLowerError::UnresolvedMethod(_)
+            | MirLowerError::UnresolvedField
+            | MirLowerError::MissingFunctionDefinition
+            | MirLowerError::TypeMismatch(_)
+            | MirLowerError::TypeError(_)
+            | MirLowerError::NotSupported(_)
+            | MirLowerError::ContinueWithoutLoop
+            | MirLowerError::BreakWithoutLoop
+            | MirLowerError::Loop
+            | MirLowerError::ImplementationError(_)
+            | MirLowerError::LangItemNotFound(_)
+            | MirLowerError::MutatingRvalue
+            | MirLowerError::UnresolvedLabel
+            | MirLowerError::UnresolvedUpvar(_) => writeln!(f, "{:?}", self)?,
+        }
+        Ok(())
+    }
+}
+
 macro_rules! not_supported {
     ($x: expr) => {
         return Err(MirLowerError::NotSupported(format!($x)))
@@ -101,15 +144,6 @@ macro_rules! implementation_error {
     }};
 }
 
-impl From<ConstEvalError> for MirLowerError {
-    fn from(value: ConstEvalError) -> Self {
-        match value {
-            ConstEvalError::MirLowerError(e) => e,
-            _ => MirLowerError::ConstEvalError(Box::new(value)),
-        }
-    }
-}
-
 impl From<LayoutError> for MirLowerError {
     fn from(value: LayoutError) -> Self {
         MirLowerError::LayoutError(value)
@@ -177,7 +211,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
         if !self.has_adjustments(expr_id) {
             match &self.body.exprs[expr_id] {
                 Expr::Literal(l) => {
-                    let ty = self.expr_ty(expr_id);
+                    let ty = self.expr_ty_without_adjust(expr_id);
                     return Ok(Some((self.lower_literal_to_operand(ty, l)?, current)));
                 }
                 _ => (),
@@ -282,7 +316,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                         {
                             match assoc {
                                 hir_def::AssocItemId::ConstId(c) => {
-                                    self.lower_const(c, current, place, subst, expr_id.into())?;
+                                    self.lower_const(c, current, place, subst, expr_id.into(), self.expr_ty_without_adjust(expr_id))?;
                                     return Ok(Some(current))
                                 },
                                 hir_def::AssocItemId::FunctionId(_) => {
@@ -309,17 +343,20 @@ impl<'ctx> MirLowerCtx<'ctx> {
                     }
                 };
                 match pr {
-                    ValueNs::LocalBinding(pat_id) => {
+                    ValueNs::LocalBinding(_) | ValueNs::StaticId(_) => {
+                        let Some((temp, current)) = self.lower_expr_as_place_without_adjust(current, expr_id, false)? else {
+                            return Ok(None);
+                        };
                         self.push_assignment(
                             current,
                             place,
-                            Operand::Copy(self.binding_local(pat_id)?.into()).into(),
+                            Operand::Copy(temp).into(),
                             expr_id.into(),
                         );
                         Ok(Some(current))
                     }
                     ValueNs::ConstId(const_id) => {
-                        self.lower_const(const_id, current, place, Substitution::empty(Interner), expr_id.into())?;
+                        self.lower_const(const_id, current, place, Substitution::empty(Interner), expr_id.into(), self.expr_ty_without_adjust(expr_id))?;
                         Ok(Some(current))
                     }
                     ValueNs::EnumVariantId(variant_id) => {
@@ -343,7 +380,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                             not_supported!("owner without generic def id");
                         };
                         let gen = generics(self.db.upcast(), def);
-                        let ty = self.expr_ty(expr_id);
+                        let ty = self.expr_ty_without_adjust(expr_id);
                         self.push_assignment(
                             current,
                             place,
@@ -388,12 +425,13 @@ impl<'ctx> MirLowerCtx<'ctx> {
                 };
                 self.set_terminator(
                     current,
-                    Terminator::SwitchInt {
+                    TerminatorKind::SwitchInt {
                         discr,
                         targets: SwitchTargets::static_if(1, start_of_then, start_of_else),
                     },
+                    expr_id.into(),
                 );
-                Ok(self.merge_blocks(end_of_then, end_of_else))
+                Ok(self.merge_blocks(end_of_then, end_of_else, expr_id.into()))
             }
             Expr::Let { pat, expr } => {
                 let Some((cond_place, current)) = self.lower_expr_as_place(current, *expr, true)? else {
@@ -423,32 +461,32 @@ impl<'ctx> MirLowerCtx<'ctx> {
                         MirSpan::Unknown,
                     )?;
                 }
-                Ok(self.merge_blocks(Some(then_target), else_target))
+                Ok(self.merge_blocks(Some(then_target), else_target, expr_id.into()))
             }
             Expr::Unsafe { id: _, statements, tail } => {
-                self.lower_block_to_place(statements, current, *tail, place)
+                self.lower_block_to_place(statements, current, *tail, place, expr_id.into())
             }
             Expr::Block { id: _, statements, tail, label } => {
                 if let Some(label) = label {
-                    self.lower_loop(current, place.clone(), Some(*label), |this, begin| {
-                        if let Some(block) = this.lower_block_to_place(statements, begin, *tail, place)? {
+                    self.lower_loop(current, place.clone(), Some(*label), expr_id.into(), |this, begin| {
+                        if let Some(block) = this.lower_block_to_place(statements, begin, *tail, place, expr_id.into())? {
                             let end = this.current_loop_end()?;
-                            this.set_goto(block, end);
+                            this.set_goto(block, end, expr_id.into());
                         }
                         Ok(())
                     })
                 } else {
-                    self.lower_block_to_place(statements, current, *tail, place)
+                    self.lower_block_to_place(statements, current, *tail, place, expr_id.into())
                 }
             }
-            Expr::Loop { body, label } => self.lower_loop(current, place, *label, |this, begin| {
+            Expr::Loop { body, label } => self.lower_loop(current, place, *label, expr_id.into(), |this, begin| {
                 if let Some((_, block)) = this.lower_expr_as_place(begin, *body, true)? {
-                    this.set_goto(block, begin);
+                    this.set_goto(block, begin, expr_id.into());
                 }
                 Ok(())
             }),
             Expr::While { condition, body, label } => {
-                self.lower_loop(current, place, *label, |this, begin| {
+                self.lower_loop(current, place, *label, expr_id.into(),|this, begin| {
                     let Some((discr, to_switch)) = this.lower_expr_to_some_operand(*condition, begin)? else {
                         return Ok(());
                     };
@@ -456,13 +494,14 @@ impl<'ctx> MirLowerCtx<'ctx> {
                     let after_cond = this.new_basic_block();
                     this.set_terminator(
                         to_switch,
-                        Terminator::SwitchInt {
+                        TerminatorKind::SwitchInt {
                             discr,
                             targets: SwitchTargets::static_if(1, after_cond, end),
                         },
+                        expr_id.into(),
                     );
                     if let Some((_, block)) = this.lower_expr_as_place(after_cond, *body, true)? {
-                        this.set_goto(block, begin);
+                        this.set_goto(block, begin, expr_id.into());
                     }
                     Ok(())
                 })
@@ -478,12 +517,12 @@ impl<'ctx> MirLowerCtx<'ctx> {
                 let into_iter_fn_op = Operand::const_zst(
                     TyKind::FnDef(
                         self.db.intern_callable_def(CallableDefId::FunctionId(into_iter_fn)).into(),
-                        Substitution::from1(Interner, self.expr_ty(iterable))
+                        Substitution::from1(Interner, self.expr_ty_without_adjust(iterable))
                     ).intern(Interner));
                 let iter_next_fn_op = Operand::const_zst(
                     TyKind::FnDef(
                         self.db.intern_callable_def(CallableDefId::FunctionId(iter_next_fn)).into(),
-                        Substitution::from1(Interner, self.expr_ty(iterable))
+                        Substitution::from1(Interner, self.expr_ty_without_adjust(iterable))
                     ).intern(Interner));
                 let &Some(iterator_ty) = &self.infer.type_of_for_iterator.get(&expr_id) else {
                     return Err(MirLowerError::TypeError("unknown for loop iterator type"));
@@ -494,13 +533,13 @@ impl<'ctx> MirLowerCtx<'ctx> {
                 let iterator_place: Place = self.temp(iterator_ty.clone())?.into();
                 let option_item_place: Place = self.temp(option_item_ty.clone())?.into();
                 let ref_mut_iterator_place: Place = self.temp(ref_mut_iterator_ty)?.into();
-                let Some(current) = self.lower_call_and_args(into_iter_fn_op, Some(iterable).into_iter(), iterator_place.clone(), current, false)?
+                let Some(current) = self.lower_call_and_args(into_iter_fn_op, Some(iterable).into_iter(), iterator_place.clone(), current, false, expr_id.into())?
                 else {
                     return Ok(None);
                 };
                 self.push_assignment(current, ref_mut_iterator_place.clone(), Rvalue::Ref(BorrowKind::Mut { allow_two_phase_borrow: false }, iterator_place), expr_id.into());
-                self.lower_loop(current, place, label, |this, begin| {
-                    let Some(current) = this.lower_call(iter_next_fn_op, vec![Operand::Copy(ref_mut_iterator_place)], option_item_place.clone(), begin, false)?
+                self.lower_loop(current, place, label, expr_id.into(), |this, begin| {
+                    let Some(current) = this.lower_call(iter_next_fn_op, vec![Operand::Copy(ref_mut_iterator_place)], option_item_place.clone(), begin, false, expr_id.into())?
                     else {
                         return Ok(());
                     };
@@ -516,7 +555,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                         AdtPatternShape::Tuple { args: &[pat], ellipsis: None },
                     )?;
                     if let Some((_, block)) = this.lower_expr_as_place(current, body, true)? {
-                        this.set_goto(block, begin);
+                        this.set_goto(block, begin, expr_id.into());
                     }
                     Ok(())
                 })
@@ -536,39 +575,36 @@ impl<'ctx> MirLowerCtx<'ctx> {
                         place,
                         current,
                         self.is_uninhabited(expr_id),
+                        expr_id.into(),
                     );
                 }
                 let callee_ty = self.expr_ty_after_adjustments(*callee);
                 match &callee_ty.data(Interner).kind {
                     chalk_ir::TyKind::FnDef(..) => {
                         let func = Operand::from_bytes(vec![], callee_ty.clone());
-                        self.lower_call_and_args(func, args.iter().copied(), place, current, self.is_uninhabited(expr_id))
+                        self.lower_call_and_args(func, args.iter().copied(), place, current, self.is_uninhabited(expr_id), expr_id.into())
                     }
                     chalk_ir::TyKind::Function(_) => {
                         let Some((func, current)) = self.lower_expr_to_some_operand(*callee, current)? else {
                             return Ok(None);
                         };
-                        self.lower_call_and_args(func, args.iter().copied(), place, current, self.is_uninhabited(expr_id))
+                        self.lower_call_and_args(func, args.iter().copied(), place, current, self.is_uninhabited(expr_id), expr_id.into())
                     }
                     TyKind::Error => return Err(MirLowerError::MissingFunctionDefinition),
                     _ => return Err(MirLowerError::TypeError("function call on bad type")),
                 }
             }
-            Expr::MethodCall { receiver, args, .. } => {
+            Expr::MethodCall { receiver, args, method_name, .. } => {
                 let (func_id, generic_args) =
-                    self.infer.method_resolution(expr_id).ok_or(MirLowerError::UnresolvedMethod)?;
-                let ty = chalk_ir::TyKind::FnDef(
-                    CallableDefId::FunctionId(func_id).to_chalk(self.db),
-                    generic_args,
-                )
-                .intern(Interner);
-                let func = Operand::from_bytes(vec![], ty);
+                    self.infer.method_resolution(expr_id).ok_or_else(|| MirLowerError::UnresolvedMethod(format!("{}", method_name)))?;
+                let func = Operand::from_fn(self.db, func_id, generic_args);
                 self.lower_call_and_args(
                     func,
                     iter::once(*receiver).chain(args.iter().copied()),
                     place,
                     current,
                     self.is_uninhabited(expr_id),
+                    expr_id.into(),
                 )
             }
             Expr::Match { expr, arms } => {
@@ -591,7 +627,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                         let next = self.new_basic_block();
                         let o = otherwise.get_or_insert_with(|| self.new_basic_block());
                         if let Some((discr, c)) = self.lower_expr_to_some_operand(guard, then)? {
-                            self.set_terminator(c, Terminator::SwitchInt { discr, targets: SwitchTargets::static_if(1, next, *o) });
+                            self.set_terminator(c, TerminatorKind::SwitchInt { discr, targets: SwitchTargets::static_if(1, next, *o) }, expr_id.into());
                         }
                         next
                     } else {
@@ -599,7 +635,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                     };
                     if let Some(block) = self.lower_expr_to_place(*expr, place.clone(), then)? {
                         let r = end.get_or_insert_with(|| self.new_basic_block());
-                        self.set_goto(block, *r);
+                        self.set_goto(block, *r, expr_id.into());
                     }
                     match otherwise {
                         Some(o) => current = o,
@@ -611,18 +647,17 @@ impl<'ctx> MirLowerCtx<'ctx> {
                     }
                 }
                 if self.is_unterminated(current) {
-                    self.set_terminator(current, Terminator::Unreachable);
+                    self.set_terminator(current, TerminatorKind::Unreachable, expr_id.into());
                 }
                 Ok(end)
             }
-            Expr::Continue { label } => match label {
-                Some(_) => not_supported!("continue with label"),
-                None => {
-                    let loop_data =
-                        self.current_loop_blocks.as_ref().ok_or(MirLowerError::ContinueWithoutLoop)?;
-                    self.set_goto(current, loop_data.begin);
-                    Ok(None)
-                }
+            Expr::Continue { label } => {
+                let loop_data = match label {
+                    Some(l) => self.labeled_loop_blocks.get(l).ok_or(MirLowerError::UnresolvedLabel)?,
+                    None => self.current_loop_blocks.as_ref().ok_or(MirLowerError::ContinueWithoutLoop)?,
+                };
+                self.set_goto(current, loop_data.begin, expr_id.into());
+                Ok(None)
             },
             &Expr::Break { expr, label } => {
                 if let Some(expr) = expr {
@@ -639,7 +674,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                     Some(l) => self.labeled_loop_blocks.get(&l).ok_or(MirLowerError::UnresolvedLabel)?.end.expect("We always generate end for labeled loops"),
                     None => self.current_loop_end()?,
                 };
-                self.set_goto(current, end);
+                self.set_goto(current, end, expr_id.into());
                 Ok(None)
             }
             Expr::Return { expr } => {
@@ -650,7 +685,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                         return Ok(None);
                     }
                 }
-                self.set_terminator(current, Terminator::Return);
+                self.set_terminator(current, TerminatorKind::Return, expr_id.into());
                 Ok(None)
             }
             Expr::Yield { .. } => not_supported!("yield"),
@@ -672,7 +707,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                         Some(p) => MirLowerError::UnresolvedName(p.display(self.db).to_string()),
                         None => MirLowerError::RecordLiteralWithoutPath,
                     })?;
-                let subst = match self.expr_ty(expr_id).kind(Interner) {
+                let subst = match self.expr_ty_without_adjust(expr_id).kind(Interner) {
                     TyKind::Adt(_, s) => s.clone(),
                     _ => not_supported!("Non ADT record literal"),
                 };
@@ -757,7 +792,17 @@ impl<'ctx> MirLowerCtx<'ctx> {
                 self.push_assignment(current, place, Rvalue::Ref(bk, p), expr_id.into());
                 Ok(Some(current))
             }
-            Expr::Box { .. } => not_supported!("box expression"),
+            Expr::Box { expr } => {
+                let ty = self.expr_ty_after_adjustments(*expr);
+                self.push_assignment(current, place.clone(), Rvalue::ShallowInitBoxWithAlloc(ty), expr_id.into());
+                let Some((operand, current)) = self.lower_expr_to_some_operand(*expr, current)? else {
+                    return Ok(None);
+                };
+                let mut p = place;
+                p.projection.push(ProjectionElem::Deref);
+                self.push_assignment(current, p, operand.into(), expr_id.into());
+                Ok(Some(current))
+            },
             Expr::Field { .. } | Expr::Index { .. } | Expr::UnaryOp { op: hir_def::hir::UnaryOp::Deref, .. } => {
                 let Some((p, current)) = self.lower_expr_as_place_without_adjust(current, expr_id, true)? else {
                     return Ok(None);
@@ -784,20 +829,63 @@ impl<'ctx> MirLowerCtx<'ctx> {
             },
             Expr::BinaryOp { lhs, rhs, op } => {
                 let op = op.ok_or(MirLowerError::IncompleteExpr)?;
-                if let hir_def::hir::BinaryOp::Assignment { op } = op {
-                    if op.is_some() {
-                        not_supported!("assignment with arith op (like +=)");
+                let is_builtin = {
+                    // Without adjust here is a hack. We assume that we know every possible adjustment
+                    // for binary operator, and use without adjust to simplify our conditions.
+                    let lhs_ty = self.expr_ty_without_adjust(*lhs);
+                    let rhs_ty = self.expr_ty_without_adjust(*rhs);
+                    let builtin_inequal_impls = matches!(
+                        op,
+                        BinaryOp::ArithOp(ArithOp::Shl | ArithOp::Shr) | BinaryOp::Assignment { op: Some(ArithOp::Shl | ArithOp::Shr) }
+                    );
+                    lhs_ty.as_builtin().is_some() && rhs_ty.as_builtin().is_some() && (lhs_ty == rhs_ty || builtin_inequal_impls)
+                };
+                if !is_builtin {
+                    if let Some((func_id, generic_args)) = self.infer.method_resolution(expr_id) {
+                        let func = Operand::from_fn(self.db, func_id, generic_args);
+                        return self.lower_call_and_args(
+                            func,
+                            [*lhs, *rhs].into_iter(),
+                            place,
+                            current,
+                            self.is_uninhabited(expr_id),
+                            expr_id.into(),
+                        );
                     }
-                    let Some((lhs_place, current)) =
+                }
+                if let hir_def::hir::BinaryOp::Assignment { op } = op {
+                    if let Some(op) = op {
+                        // last adjustment is `&mut` which we don't want it.
+                        let adjusts = self
+                            .infer
+                            .expr_adjustments
+                            .get(lhs)
+                            .and_then(|x| x.split_last())
+                            .map(|x| x.1)
+                            .ok_or(MirLowerError::TypeError("adjustment of binary op was missing"))?;
+                        let Some((lhs_place, current)) =
+                            self.lower_expr_as_place_with_adjust(current, *lhs, false, adjusts)?
+                        else {
+                            return Ok(None);
+                        };
+                        let Some((rhs_op, current)) = self.lower_expr_to_some_operand(*rhs, current)? else {
+                            return Ok(None);
+                        };
+                        let r_value = Rvalue::CheckedBinaryOp(op.into(), Operand::Copy(lhs_place.clone()), rhs_op);
+                        self.push_assignment(current, lhs_place, r_value, expr_id.into());
+                        return Ok(Some(current));
+                    } else {
+                        let Some((lhs_place, current)) =
                         self.lower_expr_as_place(current, *lhs, false)?
-                    else {
-                        return Ok(None);
-                    };
-                    let Some((rhs_op, current)) = self.lower_expr_to_some_operand(*rhs, current)? else {
-                        return Ok(None);
-                    };
-                    self.push_assignment(current, lhs_place, rhs_op.into(), expr_id.into());
-                    return Ok(Some(current));
+                        else {
+                            return Ok(None);
+                        };
+                        let Some((rhs_op, current)) = self.lower_expr_to_some_operand(*rhs, current)? else {
+                            return Ok(None);
+                        };
+                        self.push_assignment(current, lhs_place, rhs_op.into(), expr_id.into());
+                        return Ok(Some(current));
+                    }
                 }
                 let Some((lhs_op, current)) = self.lower_expr_to_some_operand(*lhs, current)? else {
                     return Ok(None);
@@ -826,7 +914,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                 Ok(Some(current))
             }
             &Expr::Range { lhs, rhs, range_type: _ } => {
-                let ty = self.expr_ty(expr_id);
+                let ty = self.expr_ty_without_adjust(expr_id);
                 let Some((adt, subst)) = ty.as_adt() else {
                     return Err(MirLowerError::TypeError("Range type is not adt"));
                 };
@@ -869,7 +957,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                 Ok(Some(current))
             },
             Expr::Closure { .. } => {
-                let ty = self.expr_ty(expr_id);
+                let ty = self.expr_ty_without_adjust(expr_id);
                 let TyKind::Closure(id, _) = ty.kind(Interner) else {
                     not_supported!("closure with non closure type");
                 };
@@ -893,7 +981,12 @@ impl<'ctx> MirLowerCtx<'ctx> {
                     };
                     match &capture.kind {
                         CaptureKind::ByRef(bk) => {
-                            let tmp: Place = self.temp(capture.ty.clone())?.into();
+                            let placeholder_subst = match self.owner.as_generic_def_id() {
+                                Some(x) => TyBuilder::placeholder_subst(self.db, x),
+                                None => Substitution::empty(Interner),
+                            };
+                            let tmp_ty = capture.ty.clone().substitute(Interner, &placeholder_subst);
+                            let tmp: Place = self.temp(tmp_ty)?.into();
                             self.push_assignment(
                                 current,
                                 tmp.clone(),
@@ -928,7 +1021,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                     return Ok(None);
                 };
                 let r = Rvalue::Aggregate(
-                    AggregateKind::Tuple(self.expr_ty(expr_id)),
+                    AggregateKind::Tuple(self.expr_ty_without_adjust(expr_id)),
                     values,
                 );
                 self.push_assignment(current, place, r, expr_id.into());
@@ -936,7 +1029,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
             }
             Expr::Array(l) => match l {
                 Array::ElementList { elements, .. } => {
-                    let elem_ty = match &self.expr_ty(expr_id).data(Interner).kind {
+                    let elem_ty = match &self.expr_ty_without_adjust(expr_id).data(Interner).kind {
                         TyKind::Array(ty, _) => ty.clone(),
                         _ => {
                             return Err(MirLowerError::TypeError(
@@ -968,7 +1061,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                     let Some((init, current)) = self.lower_expr_to_some_operand(*initializer, current)? else {
                         return Ok(None);
                     };
-                    let len = match &self.expr_ty(expr_id).data(Interner).kind {
+                    let len = match &self.expr_ty_without_adjust(expr_id).data(Interner).kind {
                         TyKind::Array(_, len) => len.clone(),
                         _ => {
                             return Err(MirLowerError::TypeError(
@@ -982,7 +1075,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                 },
             },
             Expr::Literal(l) => {
-                let ty = self.expr_ty(expr_id);
+                let ty = self.expr_ty_without_adjust(expr_id);
                 let op = self.lower_literal_to_operand(ty, l)?;
                 self.push_assignment(current, place, op.into(), expr_id.into());
                 Ok(Some(current))
@@ -1057,8 +1150,30 @@ impl<'ctx> MirLowerCtx<'ctx> {
         place: Place,
         subst: Substitution,
         span: MirSpan,
+        ty: Ty,
     ) -> Result<()> {
-        let c = self.db.const_eval(const_id, subst)?;
+        let c = if subst.len(Interner) != 0 {
+            // We can't evaluate constant with substitution now, as generics are not monomorphized in lowering.
+            intern_const_scalar(ConstScalar::UnevaluatedConst(const_id, subst), ty)
+        } else {
+            let (const_id, subst) = lookup_impl_const(
+                self.db,
+                self.db.trait_environment_for_body(self.owner),
+                const_id,
+                subst,
+            );
+            let name = self
+                .db
+                .const_data(const_id)
+                .name
+                .as_ref()
+                .and_then(|x| x.as_str())
+                .unwrap_or("_")
+                .to_owned();
+            self.db
+                .const_eval(const_id.into(), subst)
+                .map_err(|e| MirLowerError::ConstEvalError(name, Box::new(e)))?
+        };
         self.write_const_to_place(c, prev_block, place, span)
     }
 
@@ -1114,6 +1229,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
         place: Place,
         mut current: BasicBlockId,
         is_uninhabited: bool,
+        span: MirSpan,
     ) -> Result<Option<BasicBlockId>> {
         let Some(args) = args
             .map(|arg| {
@@ -1128,7 +1244,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
         else {
             return Ok(None);
         };
-        self.lower_call(func, args, place, current, is_uninhabited)
+        self.lower_call(func, args, place, current, is_uninhabited, span)
     }
 
     fn lower_call(
@@ -1138,11 +1254,12 @@ impl<'ctx> MirLowerCtx<'ctx> {
         place: Place,
         current: BasicBlockId,
         is_uninhabited: bool,
+        span: MirSpan,
     ) -> Result<Option<BasicBlockId>> {
         let b = if is_uninhabited { None } else { Some(self.new_basic_block()) };
         self.set_terminator(
             current,
-            Terminator::Call {
+            TerminatorKind::Call {
                 func,
                 args,
                 destination: place,
@@ -1150,6 +1267,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                 cleanup: None,
                 from_hir_call: true,
             },
+            span,
         );
         Ok(b)
     }
@@ -1158,15 +1276,15 @@ impl<'ctx> MirLowerCtx<'ctx> {
         self.result.basic_blocks[source].terminator.is_none()
     }
 
-    fn set_terminator(&mut self, source: BasicBlockId, terminator: Terminator) {
-        self.result.basic_blocks[source].terminator = Some(terminator);
+    fn set_terminator(&mut self, source: BasicBlockId, terminator: TerminatorKind, span: MirSpan) {
+        self.result.basic_blocks[source].terminator = Some(Terminator { span, kind: terminator });
     }
 
-    fn set_goto(&mut self, source: BasicBlockId, target: BasicBlockId) {
-        self.set_terminator(source, Terminator::Goto { target });
+    fn set_goto(&mut self, source: BasicBlockId, target: BasicBlockId, span: MirSpan) {
+        self.set_terminator(source, TerminatorKind::Goto { target }, span);
     }
 
-    fn expr_ty(&self, e: ExprId) -> Ty {
+    fn expr_ty_without_adjust(&self, e: ExprId) -> Ty {
         self.infer[e].clone()
     }
 
@@ -1177,7 +1295,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                 ty = Some(x.target.clone());
             }
         }
-        ty.unwrap_or_else(|| self.expr_ty(e))
+        ty.unwrap_or_else(|| self.expr_ty_without_adjust(e))
     }
 
     fn push_statement(&mut self, block: BasicBlockId, statement: Statement) {
@@ -1211,6 +1329,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
         prev_block: BasicBlockId,
         place: Place,
         label: Option<LabelId>,
+        span: MirSpan,
         f: impl FnOnce(&mut MirLowerCtx<'_>, BasicBlockId) -> Result<()>,
     ) -> Result<Option<BasicBlockId>> {
         let begin = self.new_basic_block();
@@ -1228,7 +1347,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
         } else {
             None
         };
-        self.set_goto(prev_block, begin);
+        self.set_goto(prev_block, begin, span);
         f(self, begin)?;
         let my = mem::replace(&mut self.current_loop_blocks, prev).ok_or(
             MirLowerError::ImplementationError("current_loop_blocks is corrupt".to_string()),
@@ -1247,14 +1366,15 @@ impl<'ctx> MirLowerCtx<'ctx> {
         &mut self,
         b1: Option<BasicBlockId>,
         b2: Option<BasicBlockId>,
+        span: MirSpan,
     ) -> Option<BasicBlockId> {
         match (b1, b2) {
             (None, None) => None,
             (None, Some(b)) | (Some(b), None) => Some(b),
             (Some(b1), Some(b2)) => {
                 let bm = self.new_basic_block();
-                self.set_goto(b1, bm);
-                self.set_goto(b2, bm);
+                self.set_goto(b1, bm, span);
+                self.set_goto(b2, bm, span);
                 Some(bm)
             }
         }
@@ -1332,6 +1452,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
         mut current: BasicBlockId,
         tail: Option<ExprId>,
         place: Place,
+        span: MirSpan,
     ) -> Result<Option<Idx<BasicBlock>>> {
         for statement in statements.iter() {
             match statement {
@@ -1355,13 +1476,13 @@ impl<'ctx> MirLowerCtx<'ctx> {
                         match (else_block, else_branch) {
                             (None, _) => (),
                             (Some(else_block), None) => {
-                                self.set_terminator(else_block, Terminator::Unreachable);
+                                self.set_terminator(else_block, TerminatorKind::Unreachable, span);
                             }
                             (Some(else_block), Some(else_branch)) => {
                                 if let Some((_, b)) =
                                     self.lower_expr_as_place(else_block, *else_branch, true)?
                                 {
-                                    self.set_terminator(b, Terminator::Unreachable);
+                                    self.set_terminator(b, TerminatorKind::Unreachable, span);
                                 }
                             }
                         }
@@ -1438,7 +1559,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
                 BindingAnnotation::Unannotated,
             )?;
             if let Some(b) = r.1 {
-                self.set_terminator(b, Terminator::Unreachable);
+                self.set_terminator(b, TerminatorKind::Unreachable, param.into());
             }
             current = r.0;
         }
@@ -1456,6 +1577,18 @@ impl<'ctx> MirLowerCtx<'ctx> {
             }
         }
     }
+
+    fn const_eval_discriminant(&self, variant: EnumVariantId) -> Result<i128> {
+        let r = self.db.const_eval_discriminant(variant);
+        match r {
+            Ok(r) => Ok(r),
+            Err(e) => {
+                let data = self.db.enum_data(variant.parent);
+                let name = format!("{}::{}", data.name, data.variants[variant.local_id].name);
+                Err(MirLowerError::ConstEvalError(name, Box::new(e)))
+            }
+        }
+    }
 }
 
 fn cast_kind(source_ty: &Ty, target_ty: &Ty) -> Result<CastKind> {
@@ -1498,7 +1631,7 @@ pub fn mir_body_for_closure_query(
     // 0 is return local
     ctx.result.locals.alloc(Local { ty: infer[*root].clone() });
     ctx.result.locals.alloc(Local { ty: infer[expr].clone() });
-    let Some(sig) = substs.at(Interner, 0).assert_ty_ref(Interner).callable_sig(db) else {
+    let Some(sig) = ClosureSubst(substs).sig_ty().callable_sig(db) else {
         implementation_error!("closure has not callable sig");
     };
     let current = ctx.lower_params_and_bindings(
@@ -1506,7 +1639,7 @@ pub fn mir_body_for_closure_query(
         |_| true,
     )?;
     if let Some(b) = ctx.lower_expr_to_place(*root, return_slot().into(), current)? {
-        ctx.set_terminator(b, Terminator::Return);
+        ctx.set_terminator(b, TerminatorKind::Return, (*root).into());
     }
     let mut upvar_map: FxHashMap<LocalId, Vec<(&CapturedItem, usize)>> = FxHashMap::default();
     for (i, capture) in captures.iter().enumerate() {
@@ -1628,7 +1761,7 @@ pub fn lower_to_mir(
         ctx.lower_params_and_bindings([].into_iter(), binding_picker)?
     };
     if let Some(b) = ctx.lower_expr_to_place(root_expr, return_slot().into(), current)? {
-        ctx.set_terminator(b, Terminator::Return);
+        ctx.set_terminator(b, TerminatorKind::Return, root_expr.into());
     }
     Ok(ctx.result)
 }
diff --git a/crates/hir-ty/src/mir/lower/as_place.rs b/crates/hir-ty/src/mir/lower/as_place.rs
index a1574f55936..8d8870da0d4 100644
--- a/crates/hir-ty/src/mir/lower/as_place.rs
+++ b/crates/hir-ty/src/mir/lower/as_place.rs
@@ -1,7 +1,7 @@
 //! MIR lowering for places
 
 use super::*;
-use hir_def::FunctionId;
+use hir_def::{lang_item::lang_attr, FunctionId};
 use hir_expand::name;
 
 macro_rules! not_supported {
@@ -16,7 +16,7 @@ impl MirLowerCtx<'_> {
         expr_id: ExprId,
         prev_block: BasicBlockId,
     ) -> Result<Option<(Place, BasicBlockId)>> {
-        let ty = self.expr_ty(expr_id);
+        let ty = self.expr_ty_without_adjust(expr_id);
         let place = self.temp(ty)?;
         let Some(current) = self.lower_expr_to_place_without_adjust(expr_id, place.into(), prev_block)? else {
             return Ok(None);
@@ -30,8 +30,10 @@ impl MirLowerCtx<'_> {
         prev_block: BasicBlockId,
         adjustments: &[Adjustment],
     ) -> Result<Option<(Place, BasicBlockId)>> {
-        let ty =
-            adjustments.last().map(|x| x.target.clone()).unwrap_or_else(|| self.expr_ty(expr_id));
+        let ty = adjustments
+            .last()
+            .map(|x| x.target.clone())
+            .unwrap_or_else(|| self.expr_ty_without_adjust(expr_id));
         let place = self.temp(ty)?;
         let Some(current) = self.lower_expr_to_place_with_adjust(expr_id, place.into(), prev_block, adjustments)? else {
             return Ok(None);
@@ -80,7 +82,7 @@ impl MirLowerCtx<'_> {
                         r,
                         rest.last()
                             .map(|x| x.target.clone())
-                            .unwrap_or_else(|| self.expr_ty(expr_id)),
+                            .unwrap_or_else(|| self.expr_ty_without_adjust(expr_id)),
                         last.target.clone(),
                         expr_id.into(),
                         match od.0 {
@@ -135,17 +137,39 @@ impl MirLowerCtx<'_> {
                 };
                 match pr {
                     ValueNs::LocalBinding(pat_id) => {
-                        Ok(Some((self.result.binding_locals[pat_id].into(), current)))
+                        Ok(Some((self.binding_local(pat_id)?.into(), current)))
+                    }
+                    ValueNs::StaticId(s) => {
+                        let ty = self.expr_ty_without_adjust(expr_id);
+                        let ref_ty =
+                            TyKind::Ref(Mutability::Not, static_lifetime(), ty).intern(Interner);
+                        let mut temp: Place = self.temp(ref_ty)?.into();
+                        self.push_assignment(
+                            current,
+                            temp.clone(),
+                            Operand::Static(s).into(),
+                            expr_id.into(),
+                        );
+                        temp.projection.push(ProjectionElem::Deref);
+                        Ok(Some((temp, current)))
                     }
                     _ => try_rvalue(self),
                 }
             }
             Expr::UnaryOp { expr, op } => match op {
                 hir_def::hir::UnaryOp::Deref => {
-                    if !matches!(
-                        self.expr_ty(*expr).kind(Interner),
-                        TyKind::Ref(..) | TyKind::Raw(..)
-                    ) {
+                    let is_builtin = match self.expr_ty_without_adjust(*expr).kind(Interner) {
+                        TyKind::Ref(..) | TyKind::Raw(..) => true,
+                        TyKind::Adt(id, _) => {
+                            if let Some(lang_item) = lang_attr(self.db.upcast(), id.0) {
+                                lang_item == LangItem::OwnedBox
+                            } else {
+                                false
+                            }
+                        }
+                        _ => false,
+                    };
+                    if !is_builtin {
                         let Some((p, current)) = self.lower_expr_as_place(current, *expr, true)? else {
                             return Ok(None);
                         };
@@ -153,7 +177,7 @@ impl MirLowerCtx<'_> {
                             current,
                             p,
                             self.expr_ty_after_adjustments(*expr),
-                            self.expr_ty(expr_id),
+                            self.expr_ty_without_adjust(expr_id),
                             expr_id.into(),
                             'b: {
                                 if let Some((f, _)) = self.infer.method_resolution(expr_id) {
@@ -198,7 +222,7 @@ impl MirLowerCtx<'_> {
                     )
                 {
                     let Some(index_fn) = self.infer.method_resolution(expr_id) else {
-                        return Err(MirLowerError::UnresolvedMethod);
+                        return Err(MirLowerError::UnresolvedMethod("[overloaded index]".to_string()));
                     };
                     let Some((base_place, current)) = self.lower_expr_as_place(current, *base, true)? else {
                         return Ok(None);
@@ -210,7 +234,7 @@ impl MirLowerCtx<'_> {
                         current,
                         base_place,
                         base_ty,
-                        self.expr_ty(expr_id),
+                        self.expr_ty_without_adjust(expr_id),
                         index_operand,
                         expr_id.into(),
                         index_fn,
@@ -266,7 +290,7 @@ impl MirLowerCtx<'_> {
             )
             .intern(Interner),
         );
-        let Some(current) = self.lower_call(index_fn_op, vec![Operand::Copy(ref_place), index_operand], result.clone(), current, false)? else {
+        let Some(current) = self.lower_call(index_fn_op, vec![Operand::Copy(ref_place), index_operand], result.clone(), current, false, span)? else {
             return Ok(None);
         };
         result.projection.push(ProjectionElem::Deref);
@@ -313,7 +337,7 @@ impl MirLowerCtx<'_> {
             .intern(Interner),
         );
         let mut result: Place = self.temp(target_ty_ref)?.into();
-        let Some(current) = self.lower_call(deref_fn_op, vec![Operand::Copy(ref_place)], result.clone(), current, false)? else {
+        let Some(current) = self.lower_call(deref_fn_op, vec![Operand::Copy(ref_place)], result.clone(), current, false, span)? else {
             return Ok(None);
         };
         result.projection.push(ProjectionElem::Deref);
diff --git a/crates/hir-ty/src/mir/lower/pattern_matching.rs b/crates/hir-ty/src/mir/lower/pattern_matching.rs
index 86c3ce9eec9..97aa3b0f215 100644
--- a/crates/hir-ty/src/mir/lower/pattern_matching.rs
+++ b/crates/hir-ty/src/mir/lower/pattern_matching.rs
@@ -1,5 +1,7 @@
 //! MIR lowering for patterns
 
+use hir_def::resolver::HasResolver;
+
 use crate::utils::pattern_matching_dereference_count;
 
 use super::*;
@@ -72,7 +74,7 @@ impl MirLowerCtx<'_> {
                         *pat,
                         binding_mode,
                     )?;
-                    self.set_goto(next, then_target);
+                    self.set_goto(next, then_target, pattern.into());
                     match next_else {
                         Some(t) => {
                             current = t;
@@ -85,13 +87,13 @@ impl MirLowerCtx<'_> {
                 }
                 if !finished {
                     let ce = *current_else.get_or_insert_with(|| self.new_basic_block());
-                    self.set_goto(current, ce);
+                    self.set_goto(current, ce, pattern.into());
                 }
                 (then_target, current_else)
             }
             Pat::Record { args, .. } => {
                 let Some(variant) = self.infer.variant_resolution_for_pat(pattern) else {
-                    not_supported!("unresolved variant");
+                    not_supported!("unresolved variant for record");
                 };
                 self.pattern_matching_variant(
                     cond_ty,
@@ -106,11 +108,8 @@ impl MirLowerCtx<'_> {
             }
             Pat::Range { .. } => not_supported!("range pattern"),
             Pat::Slice { .. } => not_supported!("slice pattern"),
-            Pat::Path(_) => {
-                let Some(variant) = self.infer.variant_resolution_for_pat(pattern) else {
-                    not_supported!("unresolved variant");
-                };
-                self.pattern_matching_variant(
+            Pat::Path(p) => match self.infer.variant_resolution_for_pat(pattern) {
+                Some(variant) => self.pattern_matching_variant(
                     cond_ty,
                     binding_mode,
                     cond_place,
@@ -119,8 +118,60 @@ impl MirLowerCtx<'_> {
                     pattern.into(),
                     current_else,
                     AdtPatternShape::Unit,
-                )?
-            }
+                )?,
+                None => {
+                    let unresolved_name = || MirLowerError::unresolved_path(self.db, p);
+                    let resolver = self.owner.resolver(self.db.upcast());
+                    let pr = resolver
+                        .resolve_path_in_value_ns(self.db.upcast(), p)
+                        .ok_or_else(unresolved_name)?;
+                    match pr {
+                        ResolveValueResult::ValueNs(v) => match v {
+                            ValueNs::ConstId(c) => {
+                                let tmp: Place = self.temp(cond_ty.clone())?.into();
+                                let span = pattern.into();
+                                self.lower_const(
+                                    c,
+                                    current,
+                                    tmp.clone(),
+                                    Substitution::empty(Interner),
+                                    span,
+                                    cond_ty.clone(),
+                                )?;
+                                let tmp2: Place = self.temp(TyBuilder::bool())?.into();
+                                self.push_assignment(
+                                    current,
+                                    tmp2.clone(),
+                                    Rvalue::CheckedBinaryOp(
+                                        BinOp::Eq,
+                                        Operand::Copy(tmp),
+                                        Operand::Copy(cond_place),
+                                    ),
+                                    span,
+                                );
+                                let next = self.new_basic_block();
+                                let else_target =
+                                    current_else.unwrap_or_else(|| self.new_basic_block());
+                                self.set_terminator(
+                                    current,
+                                    TerminatorKind::SwitchInt {
+                                        discr: Operand::Copy(tmp2),
+                                        targets: SwitchTargets::static_if(1, next, else_target),
+                                    },
+                                    span,
+                                );
+                                (next, Some(else_target))
+                            }
+                            _ => not_supported!(
+                                "path in pattern position that is not const or variant"
+                            ),
+                        },
+                        ResolveValueResult::Partial(_, _) => {
+                            not_supported!("assoc const in patterns")
+                        }
+                    }
+                }
+            },
             Pat::Lit(l) => match &self.body.exprs[*l] {
                 Expr::Literal(l) => {
                     let c = self.lower_literal_to_operand(cond_ty, l)?;
@@ -218,10 +269,11 @@ impl MirLowerCtx<'_> {
         let discr = Operand::Copy(discr);
         self.set_terminator(
             current,
-            Terminator::SwitchInt {
+            TerminatorKind::SwitchInt {
                 discr,
                 targets: SwitchTargets::static_if(1, then_target, else_target),
             },
+            pattern.into(),
         );
         Ok((then_target, Some(else_target)))
     }
@@ -244,8 +296,7 @@ impl MirLowerCtx<'_> {
         };
         Ok(match variant {
             VariantId::EnumVariantId(v) => {
-                let e = self.db.const_eval_discriminant(v)? as u128;
-                let next = self.new_basic_block();
+                let e = self.const_eval_discriminant(v)? as u128;
                 let tmp = self.discr_temp_place();
                 self.push_assignment(
                     current,
@@ -253,13 +304,15 @@ impl MirLowerCtx<'_> {
                     Rvalue::Discriminant(cond_place.clone()),
                     span,
                 );
+                let next = self.new_basic_block();
                 let else_target = current_else.unwrap_or_else(|| self.new_basic_block());
                 self.set_terminator(
                     current,
-                    Terminator::SwitchInt {
+                    TerminatorKind::SwitchInt {
                         discr: Operand::Copy(tmp),
                         targets: SwitchTargets::static_if(e, next, else_target),
                     },
+                    span,
                 );
                 let enum_data = self.db.enum_data(v.parent);
                 self.pattern_matching_variant_fields(
diff --git a/crates/hir-ty/src/mir/pretty.rs b/crates/hir-ty/src/mir/pretty.rs
index a7dff396135..257860968c4 100644
--- a/crates/hir-ty/src/mir/pretty.rs
+++ b/crates/hir-ty/src/mir/pretty.rs
@@ -11,19 +11,52 @@ use la_arena::ArenaMap;
 
 use crate::{
     db::HirDatabase,
-    display::HirDisplay,
-    mir::{PlaceElem, ProjectionElem, StatementKind, Terminator},
+    display::{ClosureStyle, HirDisplay},
+    mir::{PlaceElem, ProjectionElem, StatementKind, TerminatorKind},
+    ClosureId,
 };
 
 use super::{
     AggregateKind, BasicBlockId, BorrowKind, LocalId, MirBody, Operand, Place, Rvalue, UnOp,
 };
 
+macro_rules! w {
+    ($dst:expr, $($arg:tt)*) => {
+        { let _ = write!($dst, $($arg)*); }
+    };
+}
+
+macro_rules! wln {
+    ($dst:expr) => {
+        { let _ = writeln!($dst); }
+    };
+    ($dst:expr, $($arg:tt)*) => {
+        { let _ = writeln!($dst, $($arg)*); }
+    };
+}
+
 impl MirBody {
     pub fn pretty_print(&self, db: &dyn HirDatabase) -> String {
         let hir_body = db.body(self.owner);
         let mut ctx = MirPrettyCtx::new(self, &hir_body, db);
-        ctx.for_body(ctx.body.owner);
+        ctx.for_body(|this| match ctx.body.owner {
+            hir_def::DefWithBodyId::FunctionId(id) => {
+                let data = db.function_data(id);
+                w!(this, "fn {}() ", data.name);
+            }
+            hir_def::DefWithBodyId::StaticId(id) => {
+                let data = db.static_data(id);
+                w!(this, "static {}: _ = ", data.name);
+            }
+            hir_def::DefWithBodyId::ConstId(id) => {
+                let data = db.const_data(id);
+                w!(this, "const {}: _ = ", data.name.as_ref().unwrap_or(&Name::missing()));
+            }
+            hir_def::DefWithBodyId::VariantId(id) => {
+                let data = db.enum_data(id.parent);
+                w!(this, "enum {} = ", data.name);
+            }
+        });
         ctx.result
     }
 
@@ -49,21 +82,6 @@ struct MirPrettyCtx<'a> {
     local_to_binding: ArenaMap<LocalId, BindingId>,
 }
 
-macro_rules! w {
-    ($dst:expr, $($arg:tt)*) => {
-        { let _ = write!($dst, $($arg)*); }
-    };
-}
-
-macro_rules! wln {
-    ($dst:expr) => {
-        { let _ = writeln!($dst); }
-    };
-    ($dst:expr, $($arg:tt)*) => {
-        { let _ = writeln!($dst, $($arg)*); }
-    };
-}
-
 impl Write for MirPrettyCtx<'_> {
     fn write_str(&mut self, s: &str) -> std::fmt::Result {
         let mut it = s.split('\n'); // note: `.lines()` is wrong here
@@ -91,36 +109,40 @@ impl Display for LocalName {
 }
 
 impl<'a> MirPrettyCtx<'a> {
-    fn for_body(&mut self, name: impl Debug) {
-        wln!(self, "// {:?}", name);
+    fn for_body(&mut self, name: impl FnOnce(&mut MirPrettyCtx<'_>)) {
+        name(self);
         self.with_block(|this| {
             this.locals();
             wln!(this);
             this.blocks();
         });
         for &closure in &self.body.closures {
-            let body = match self.db.mir_body_for_closure(closure) {
-                Ok(x) => x,
-                Err(e) => {
-                    wln!(self, "// error in {closure:?}: {e:?}");
-                    continue;
-                }
-            };
-            let result = mem::take(&mut self.result);
-            let indent = mem::take(&mut self.indent);
-            let mut ctx = MirPrettyCtx {
-                body: &body,
-                local_to_binding: body.binding_locals.iter().map(|(x, y)| (*y, x)).collect(),
-                result,
-                indent,
-                ..*self
-            };
-            ctx.for_body(closure);
-            self.result = ctx.result;
-            self.indent = ctx.indent;
+            self.for_closure(closure);
         }
     }
 
+    fn for_closure(&mut self, closure: ClosureId) {
+        let body = match self.db.mir_body_for_closure(closure) {
+            Ok(x) => x,
+            Err(e) => {
+                wln!(self, "// error in {closure:?}: {e:?}");
+                return;
+            }
+        };
+        let result = mem::take(&mut self.result);
+        let indent = mem::take(&mut self.indent);
+        let mut ctx = MirPrettyCtx {
+            body: &body,
+            local_to_binding: body.binding_locals.iter().map(|(x, y)| (*y, x)).collect(),
+            result,
+            indent,
+            ..*self
+        };
+        ctx.for_body(|this| wln!(this, "// Closure: {:?}", closure));
+        self.result = ctx.result;
+        self.indent = ctx.indent;
+    }
+
     fn with_block(&mut self, f: impl FnOnce(&mut MirPrettyCtx<'_>)) {
         self.indent += "    ";
         wln!(self, "{{");
@@ -155,7 +177,7 @@ impl<'a> MirPrettyCtx<'a> {
 
     fn locals(&mut self) {
         for (id, local) in self.body.locals.iter() {
-            wln!(self, "let {}: {};", self.local_name(id), local.ty.display(self.db));
+            wln!(self, "let {}: {};", self.local_name(id), self.hir_display(&local.ty));
         }
     }
 
@@ -198,11 +220,11 @@ impl<'a> MirPrettyCtx<'a> {
                     }
                 }
                 match &block.terminator {
-                    Some(terminator) => match terminator {
-                        Terminator::Goto { target } => {
+                    Some(terminator) => match &terminator.kind {
+                        TerminatorKind::Goto { target } => {
                             wln!(this, "goto 'bb{};", u32::from(target.into_raw()))
                         }
-                        Terminator::SwitchInt { discr, targets } => {
+                        TerminatorKind::SwitchInt { discr, targets } => {
                             w!(this, "switch ");
                             this.operand(discr);
                             w!(this, " ");
@@ -213,7 +235,7 @@ impl<'a> MirPrettyCtx<'a> {
                                 wln!(this, "_ => {},", this.basic_block_id(targets.otherwise()));
                             });
                         }
-                        Terminator::Call { func, args, destination, target, .. } => {
+                        TerminatorKind::Call { func, args, destination, target, .. } => {
                             w!(this, "Call ");
                             this.with_block(|this| {
                                 w!(this, "func: ");
@@ -295,7 +317,8 @@ impl<'a> MirPrettyCtx<'a> {
                 // equally. Feel free to change it.
                 self.place(p);
             }
-            Operand::Constant(c) => w!(self, "Const({})", c.display(self.db)),
+            Operand::Constant(c) => w!(self, "Const({})", self.hir_display(c)),
+            Operand::Static(s) => w!(self, "Static({:?})", s),
         }
     }
 
@@ -349,7 +372,7 @@ impl<'a> MirPrettyCtx<'a> {
             Rvalue::Cast(ck, op, ty) => {
                 w!(self, "Cast({ck:?}, ");
                 self.operand(op);
-                w!(self, ", {})", ty.display(self.db));
+                w!(self, ", {})", self.hir_display(ty));
             }
             Rvalue::CheckedBinaryOp(b, o1, o2) => {
                 self.operand(o1);
@@ -369,6 +392,7 @@ impl<'a> MirPrettyCtx<'a> {
                 self.place(p);
                 w!(self, ")");
             }
+            Rvalue::ShallowInitBoxWithAlloc(_) => w!(self, "ShallowInitBoxWithAlloc"),
             Rvalue::ShallowInitBox(op, _) => {
                 w!(self, "ShallowInitBox(");
                 self.operand(op);
@@ -392,4 +416,8 @@ impl<'a> MirPrettyCtx<'a> {
             }
         }
     }
+
+    fn hir_display<T: HirDisplay>(&self, ty: &'a T) -> impl Display + 'a {
+        ty.display(self.db).with_closure_style(ClosureStyle::ClosureWithId)
+    }
 }
diff --git a/crates/hir-ty/src/utils.rs b/crates/hir-ty/src/utils.rs
index 3b2a726688d..aa40d084795 100644
--- a/crates/hir-ty/src/utils.rs
+++ b/crates/hir-ty/src/utils.rs
@@ -23,10 +23,11 @@ use hir_expand::name::Name;
 use intern::Interned;
 use rustc_hash::FxHashSet;
 use smallvec::{smallvec, SmallVec};
+use stdx::never;
 
 use crate::{
-    db::HirDatabase, ChalkTraitId, Interner, Substitution, TraitRef, TraitRefExt, Ty, TyExt,
-    WhereClause,
+    db::HirDatabase, ChalkTraitId, GenericArg, Interner, Substitution, TraitRef, TraitRefExt, Ty,
+    TyExt, WhereClause,
 };
 
 pub(crate) fn fn_traits(
@@ -176,6 +177,37 @@ pub(crate) fn generics(db: &dyn DefDatabase, def: GenericDefId) -> Generics {
     Generics { def, params: db.generic_params(def), parent_generics }
 }
 
+/// It is a bit different from the rustc equivalent. Currently it stores:
+/// - 0: the function signature, encoded as a function pointer type
+/// - 1..n: generics of the parent
+///
+/// and it doesn't store the closure types and fields.
+///
+/// Codes should not assume this ordering, and should always use methods available
+/// on this struct for retriving, and `TyBuilder::substs_for_closure` for creating.
+pub(crate) struct ClosureSubst<'a>(pub(crate) &'a Substitution);
+
+impl<'a> ClosureSubst<'a> {
+    pub(crate) fn parent_subst(&self) -> &'a [GenericArg] {
+        match self.0.as_slice(Interner) {
+            [_, x @ ..] => x,
+            _ => {
+                never!("Closure missing parameter");
+                &[]
+            }
+        }
+    }
+
+    pub(crate) fn sig_ty(&self) -> &'a Ty {
+        match self.0.as_slice(Interner) {
+            [x, ..] => x.assert_ty_ref(Interner),
+            _ => {
+                unreachable!("Closure missing sig_ty parameter");
+            }
+        }
+    }
+}
+
 #[derive(Debug)]
 pub(crate) struct Generics {
     def: GenericDefId,
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index f7a14bf36ad..145506a89df 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -1856,11 +1856,21 @@ impl Function {
         def_map.fn_as_proc_macro(self.id).map(|id| Macro { id: id.into() })
     }
 
-    pub fn eval(self, db: &dyn HirDatabase) -> Result<(), MirEvalError> {
+    pub fn eval(
+        self,
+        db: &dyn HirDatabase,
+        span_formatter: impl Fn(FileId, TextRange) -> String,
+    ) -> Result<(), String> {
+        let converter = |e: MirEvalError| {
+            let mut r = String::new();
+            _ = e.pretty_print(&mut r, db, &span_formatter);
+            r
+        };
         let body = db
             .mir_body(self.id.into())
-            .map_err(|e| MirEvalError::MirLowerError(self.id.into(), e))?;
-        interpret_mir(db, &body, Substitution::empty(Interner), false)?;
+            .map_err(|e| MirEvalError::MirLowerError(self.id.into(), e))
+            .map_err(converter)?;
+        interpret_mir(db, &body, Substitution::empty(Interner), false).map_err(converter)?;
         Ok(())
     }
 }
@@ -2006,7 +2016,7 @@ impl Const {
     }
 
     pub fn render_eval(self, db: &dyn HirDatabase) -> Result<String, ConstEvalError> {
-        let c = db.const_eval(self.id, Substitution::empty(Interner))?;
+        let c = db.const_eval(self.id.into(), Substitution::empty(Interner))?;
         let r = format!("{}", HexifiedConst(c).display(db));
         // We want to see things like `<utf8-error>` and `<layout-error>` as they are probably bug in our
         // implementation, but there is no need to show things like `<enum-not-supported>` or `<ref-not-supported>` to
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index bbbf39ca15b..8e0aa9df147 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -30,7 +30,6 @@ pub struct HoverConfig {
     pub documentation: bool,
     pub keywords: bool,
     pub format: HoverDocFormat,
-    pub interpret_tests: bool,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
diff --git a/crates/ide/src/hover/render.rs b/crates/ide/src/hover/render.rs
index e5019b71595..8f8cdcce515 100644
--- a/crates/ide/src/hover/render.rs
+++ b/crates/ide/src/hover/render.rs
@@ -3,8 +3,7 @@ use std::fmt::Display;
 
 use either::Either;
 use hir::{
-    db::DefDatabase, Adt, AsAssocItem, AttributeTemplate, HasAttrs, HasSource, HirDisplay,
-    MirEvalError, Semantics, TypeInfo,
+    Adt, AsAssocItem, AttributeTemplate, HasAttrs, HasSource, HirDisplay, Semantics, TypeInfo,
 };
 use ide_db::{
     base_db::SourceDatabase,
@@ -435,19 +434,7 @@ pub(super) fn definition(
             ))
         }),
         Definition::Module(it) => label_and_docs(db, it),
-        Definition::Function(it) => label_and_layout_info_and_docs(db, it, |_| {
-            if !config.interpret_tests {
-                return None;
-            }
-            match it.eval(db) {
-                Ok(()) => Some("pass".into()),
-                Err(MirEvalError::MirLowerError(f, e)) => {
-                    let name = &db.function_data(f).name;
-                    Some(format!("error: fail to lower {name} due {e:?}"))
-                }
-                Err(e) => Some(format!("error: {e:?}")),
-            }
-        }),
+        Definition::Function(it) => label_and_docs(db, it),
         Definition::Adt(it) => label_and_layout_info_and_docs(db, it, |&it| {
             let layout = it.layout(db).ok()?;
             Some(format!("size = {}, align = {}", layout.size.bytes(), layout.align.abi.bytes()))
diff --git a/crates/ide/src/hover/tests.rs b/crates/ide/src/hover/tests.rs
index 24c39ab03d5..082e5372d42 100644
--- a/crates/ide/src/hover/tests.rs
+++ b/crates/ide/src/hover/tests.rs
@@ -9,7 +9,6 @@ const HOVER_BASE_CONFIG: HoverConfig = HoverConfig {
     documentation: true,
     format: HoverDocFormat::Markdown,
     keywords: true,
-    interpret_tests: false,
 };
 
 fn check_hover_no_result(ra_fixture: &str) {
diff --git a/crates/ide/src/inlay_hints/adjustment.rs b/crates/ide/src/inlay_hints/adjustment.rs
index d5be0c5b883..27e9ba3c36b 100644
--- a/crates/ide/src/inlay_hints/adjustment.rs
+++ b/crates/ide/src/inlay_hints/adjustment.rs
@@ -3,7 +3,10 @@
 //! let _: u32  = /* <never-to-any> */ loop {};
 //! let _: &u32 = /* &* */ &mut 0;
 //! ```
-use hir::{Adjust, Adjustment, AutoBorrow, HirDisplay, Mutability, PointerCast, Safety, Semantics};
+use hir::{
+    Adjust, Adjustment, AutoBorrow, HirDisplay, Mutability, OverloadedDeref, PointerCast, Safety,
+    Semantics,
+};
 use ide_db::RootDatabase;
 
 use stdx::never;
@@ -88,7 +91,13 @@ pub(super) fn hints(
             Adjust::NeverToAny if config.adjustment_hints == AdjustmentHints::Always => {
                 ("<never-to-any>", "never to any")
             }
-            Adjust::Deref(_) => ("*", "dereference"),
+            Adjust::Deref(None) => ("*", "dereference"),
+            Adjust::Deref(Some(OverloadedDeref(Mutability::Shared))) => {
+                ("*", "`Deref` dereference")
+            }
+            Adjust::Deref(Some(OverloadedDeref(Mutability::Mut))) => {
+                ("*", "`DerefMut` dereference")
+            }
             Adjust::Borrow(AutoBorrow::Ref(Mutability::Shared)) => ("&", "borrow"),
             Adjust::Borrow(AutoBorrow::Ref(Mutability::Mut)) => ("&mut ", "unique borrow"),
             Adjust::Borrow(AutoBorrow::RawPtr(Mutability::Shared)) => {
diff --git a/crates/ide/src/inlay_hints/chaining.rs b/crates/ide/src/inlay_hints/chaining.rs
index 069edaed665..d8c8401af77 100644
--- a/crates/ide/src/inlay_hints/chaining.rs
+++ b/crates/ide/src/inlay_hints/chaining.rs
@@ -444,7 +444,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 5768..5776,
+                                        range: 5769..5777,
                                     },
                                 ),
                                 tooltip: "",
@@ -457,7 +457,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 5800..5804,
+                                        range: 5801..5805,
                                     },
                                 ),
                                 tooltip: "",
@@ -478,7 +478,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 5768..5776,
+                                        range: 5769..5777,
                                     },
                                 ),
                                 tooltip: "",
@@ -491,7 +491,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 5800..5804,
+                                        range: 5801..5805,
                                     },
                                 ),
                                 tooltip: "",
@@ -512,7 +512,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 5768..5776,
+                                        range: 5769..5777,
                                     },
                                 ),
                                 tooltip: "",
@@ -525,7 +525,7 @@ fn main() {
                                         file_id: FileId(
                                             1,
                                         ),
-                                        range: 5800..5804,
+                                        range: 5801..5805,
                                     },
                                 ),
                                 tooltip: "",
diff --git a/crates/ide/src/interpret_function.rs b/crates/ide/src/interpret_function.rs
new file mode 100644
index 00000000000..d111f98955a
--- /dev/null
+++ b/crates/ide/src/interpret_function.rs
@@ -0,0 +1,49 @@
+use hir::Semantics;
+use ide_db::base_db::SourceDatabaseExt;
+use ide_db::RootDatabase;
+use ide_db::{base_db::FilePosition, LineIndexDatabase};
+use std::{fmt::Write, time::Instant};
+use syntax::TextRange;
+use syntax::{algo::find_node_at_offset, ast, AstNode};
+
+// Feature: Interpret Function
+//
+// |===
+// | Editor  | Action Name
+//
+// | VS Code | **rust-analyzer: Interpret Function**
+// |===
+pub(crate) fn interpret_function(db: &RootDatabase, position: FilePosition) -> String {
+    let start_time = Instant::now();
+    let mut result = find_and_interpret(db, position)
+        .unwrap_or_else(|| "Not inside a function body".to_string());
+    let duration = Instant::now() - start_time;
+    writeln!(result, "").unwrap();
+    writeln!(result, "----------------------").unwrap();
+    writeln!(result, "  Finished in {}s", duration.as_secs_f32()).unwrap();
+    result
+}
+
+fn find_and_interpret(db: &RootDatabase, position: FilePosition) -> Option<String> {
+    let sema = Semantics::new(db);
+    let source_file = sema.parse(position.file_id);
+
+    let item = find_node_at_offset::<ast::Item>(source_file.syntax(), position.offset)?;
+    let def = match item {
+        ast::Item::Fn(it) => sema.to_def(&it)?,
+        _ => return None,
+    };
+    let span_formatter = |file_id, text_range: TextRange| {
+        let line_col = db.line_index(file_id).line_col(text_range.start());
+        let path = &db
+            .source_root(db.file_source_root(file_id))
+            .path_for_file(&file_id)
+            .map(|x| x.to_string());
+        let path = path.as_deref().unwrap_or("<unknown file>");
+        format!("file://{path}#{}:{}", line_col.line + 1, line_col.col)
+    };
+    match def.eval(db, span_formatter) {
+        Ok(_) => Some("pass".to_string()),
+        Err(e) => Some(e),
+    }
+}
diff --git a/crates/ide/src/lib.rs b/crates/ide/src/lib.rs
index d14cf83f0d7..3509dee0c96 100644
--- a/crates/ide/src/lib.rs
+++ b/crates/ide/src/lib.rs
@@ -56,6 +56,7 @@ mod typing;
 mod view_crate_graph;
 mod view_hir;
 mod view_mir;
+mod interpret_function;
 mod view_item_tree;
 mod shuffle_crate_graph;
 
@@ -317,6 +318,10 @@ impl Analysis {
         self.with_db(|db| view_mir::view_mir(db, position))
     }
 
+    pub fn interpret_function(&self, position: FilePosition) -> Cancellable<String> {
+        self.with_db(|db| interpret_function::interpret_function(db, position))
+    }
+
     pub fn view_item_tree(&self, file_id: FileId) -> Cancellable<String> {
         self.with_db(|db| view_item_tree::view_item_tree(db, file_id))
     }
diff --git a/crates/ide/src/static_index.rs b/crates/ide/src/static_index.rs
index 774b07775b9..7ce20e973bb 100644
--- a/crates/ide/src/static_index.rs
+++ b/crates/ide/src/static_index.rs
@@ -140,7 +140,6 @@ impl StaticIndex<'_> {
             documentation: true,
             keywords: true,
             format: crate::HoverDocFormat::Markdown,
-            interpret_tests: false,
         };
         let tokens = tokens.filter(|token| {
             matches!(
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index c24bdab78a9..f9288f01b53 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -574,6 +574,7 @@ pub struct LensConfig {
     // runnables
     pub run: bool,
     pub debug: bool,
+    pub interpret: bool,
 
     // implementations
     pub implementations: bool,
@@ -1423,6 +1424,9 @@ impl Config {
         LensConfig {
             run: self.data.lens_enable && self.data.lens_run_enable,
             debug: self.data.lens_enable && self.data.lens_debug_enable,
+            interpret: self.data.lens_enable
+                && self.data.lens_run_enable
+                && self.data.interpret_tests,
             implementations: self.data.lens_enable && self.data.lens_implementations_enable,
             method_refs: self.data.lens_enable && self.data.lens_references_method_enable,
             refs_adt: self.data.lens_enable && self.data.lens_references_adt_enable,
@@ -1481,7 +1485,6 @@ impl Config {
                 }
             },
             keywords: self.data.hover_documentation_keywords_enable,
-            interpret_tests: self.data.interpret_tests,
         }
     }
 
diff --git a/crates/rust-analyzer/src/handlers.rs b/crates/rust-analyzer/src/handlers.rs
index 3c39f205e74..a5b9004d80f 100644
--- a/crates/rust-analyzer/src/handlers.rs
+++ b/crates/rust-analyzer/src/handlers.rs
@@ -163,6 +163,16 @@ pub(crate) fn handle_view_mir(
     Ok(res)
 }
 
+pub(crate) fn handle_interpret_function(
+    snap: GlobalStateSnapshot,
+    params: lsp_types::TextDocumentPositionParams,
+) -> Result<String> {
+    let _p = profile::span("handle_interpret_function");
+    let position = from_proto::file_position(&snap, params)?;
+    let res = snap.analysis.interpret_function(position)?;
+    Ok(res)
+}
+
 pub(crate) fn handle_view_file_text(
     snap: GlobalStateSnapshot,
     params: lsp_types::TextDocumentIdentifier,
diff --git a/crates/rust-analyzer/src/lsp_ext.rs b/crates/rust-analyzer/src/lsp_ext.rs
index 75309466762..90c9b16ec2b 100644
--- a/crates/rust-analyzer/src/lsp_ext.rs
+++ b/crates/rust-analyzer/src/lsp_ext.rs
@@ -90,6 +90,14 @@ impl Request for ViewMir {
     const METHOD: &'static str = "rust-analyzer/viewMir";
 }
 
+pub enum InterpretFunction {}
+
+impl Request for InterpretFunction {
+    type Params = lsp_types::TextDocumentPositionParams;
+    type Result = String;
+    const METHOD: &'static str = "rust-analyzer/interpretFunction";
+}
+
 pub enum ViewFileText {}
 
 impl Request for ViewFileText {
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 1c2b2627700..6f31c641222 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -665,6 +665,7 @@ impl GlobalState {
             .on::<lsp_ext::SyntaxTree>(handlers::handle_syntax_tree)
             .on::<lsp_ext::ViewHir>(handlers::handle_view_hir)
             .on::<lsp_ext::ViewMir>(handlers::handle_view_mir)
+            .on::<lsp_ext::InterpretFunction>(handlers::handle_interpret_function)
             .on::<lsp_ext::ViewFileText>(handlers::handle_view_file_text)
             .on::<lsp_ext::ViewCrateGraph>(handlers::handle_view_crate_graph)
             .on::<lsp_ext::ViewItemTree>(handlers::handle_view_item_tree)
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index b0b8d38cdc3..521db6b0ca9 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -1215,6 +1215,14 @@ pub(crate) fn code_lens(
                     data: None,
                 })
             }
+            if lens_config.interpret {
+                let command = command::interpret_single(&r);
+                acc.push(lsp_types::CodeLens {
+                    range: annotation_range,
+                    command: Some(command),
+                    data: None,
+                })
+            }
         }
         AnnotationKind::HasImpls { pos: file_range, data } => {
             if !client_commands_config.show_reference {
@@ -1359,6 +1367,15 @@ pub(crate) mod command {
         }
     }
 
+    pub(crate) fn interpret_single(_runnable: &lsp_ext::Runnable) -> lsp_types::Command {
+        lsp_types::Command {
+            title: "Interpret".into(),
+            command: "rust-analyzer.interpretFunction".into(),
+            // FIXME: use the `_runnable` here.
+            arguments: Some(vec![]),
+        }
+    }
+
     pub(crate) fn goto_location(
         snap: &GlobalStateSnapshot,
         nav: &NavigationTarget,
diff --git a/crates/test-utils/src/minicore.rs b/crates/test-utils/src/minicore.rs
index ca1dbf532c3..f403ef8ee03 100644
--- a/crates/test-utils/src/minicore.rs
+++ b/crates/test-utils/src/minicore.rs
@@ -11,6 +11,7 @@
 //!     add:
 //!     as_ref: sized
 //!     bool_impl: option, fn
+//!     cell: copy, drop
 //!     clone: sized
 //!     coerce_unsized: unsize
 //!     copy: clone
@@ -139,6 +140,52 @@ pub mod hash {
 }
 // endregion:hash
 
+// region:cell
+pub mod cell {
+    use crate::mem;
+
+    #[lang = "unsafe_cell"]
+    pub struct UnsafeCell<T: ?Sized> {
+        value: T,
+    }
+
+    impl<T> UnsafeCell<T> {
+        pub const fn new(value: T) -> UnsafeCell<T> {
+            UnsafeCell { value }
+        }
+
+        pub const fn get(&self) -> *mut T {
+            self as *const UnsafeCell<T> as *const T as *mut T
+        }
+    }
+
+    pub struct Cell<T: ?Sized> {
+        value: UnsafeCell<T>,
+    }
+
+    impl<T> Cell<T> {
+        pub const fn new(value: T) -> Cell<T> {
+            Cell { value: UnsafeCell::new(value) }
+        }
+
+        pub fn set(&self, val: T) {
+            let old = self.replace(val);
+            mem::drop(old);
+        }
+
+        pub fn replace(&self, val: T) -> T {
+            mem::replace(unsafe { &mut *self.value.get() }, val)
+        }
+    }
+
+    impl<T: Copy> Cell<T> {
+        pub fn get(&self) -> T {
+            unsafe { *self.value.get() }
+        }
+    }
+}
+// endregion:cell
+
 // region:clone
 pub mod clone {
     #[lang = "clone"]
@@ -220,6 +267,13 @@ pub mod mem {
     // endregion:manually_drop
 
     pub fn drop<T>(_x: T) {}
+    pub const fn replace<T>(dest: &mut T, src: T) -> T {
+        unsafe {
+            let result = *dest;
+            *dest = src;
+            result
+        }
+    }
 }
 // endregion:drop
 
@@ -710,6 +764,14 @@ pub mod option {
                 None => default,
             }
         }
+        // region:result
+        pub const fn ok_or<E>(self, err: E) -> Result<T, E> {
+            match self {
+                Some(v) => Ok(v),
+                None => Err(err),
+            }
+        }
+        // endregion:result
         // region:fn
         pub fn and_then<U, F>(self, f: F) -> Option<U>
         where
diff --git a/docs/dev/lsp-extensions.md b/docs/dev/lsp-extensions.md
index d748400b695..76080eca4e0 100644
--- a/docs/dev/lsp-extensions.md
+++ b/docs/dev/lsp-extensions.md
@@ -1,5 +1,5 @@
 <!---
-lsp_ext.rs hash: be2f663a78beb7bd
+lsp_ext.rs hash: 37ac44a0f507e05a
 
 If you need to change the above hash to make the test pass, please check if you
 need to adjust this doc as well and ping this issue:
@@ -548,6 +548,18 @@ For debugging or when working on rust-analyzer itself.
 Returns a textual representation of the MIR of the function containing the cursor.
 For debugging or when working on rust-analyzer itself.
 
+## Interpret Function
+
+**Method:** `rust-analyzer/interpretFunction`
+
+**Request:** `TextDocumentPositionParams`
+
+**Response:** `string`
+
+Tries to evaluate the function using internal rust analyzer knowledge, without compiling
+the code. Currently evaluates the function under cursor, but will give a runnable in
+future. Highly experimental.
+
 ## View File Text
 
 **Method:** `rust-analyzer/viewFileText`
diff --git a/editors/code/package.json b/editors/code/package.json
index 79e2c62e823..d46c248cd49 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -121,6 +121,11 @@
                 "category": "rust-analyzer (debug command)"
             },
             {
+                "command": "rust-analyzer.interpretFunction",
+                "title": "Interpret Function",
+                "category": "rust-analyzer (debug command)"
+            },
+            {
                 "command": "rust-analyzer.viewFileText",
                 "title": "View File Text (as seen by the server)",
                 "category": "rust-analyzer (debug command)"
diff --git a/editors/code/src/commands.ts b/editors/code/src/commands.ts
index 0d91548b9b3..2d5272d199d 100644
--- a/editors/code/src/commands.ts
+++ b/editors/code/src/commands.ts
@@ -422,8 +422,20 @@ export function syntaxTree(ctx: CtxInit): Cmd {
 function viewHirOrMir(ctx: CtxInit, xir: "hir" | "mir"): Cmd {
     const viewXir = xir === "hir" ? "viewHir" : "viewMir";
     const requestType = xir === "hir" ? ra.viewHir : ra.viewMir;
+    const uri = `rust-analyzer-${xir}://${viewXir}/${xir}.rs`;
+    const scheme = `rust-analyzer-${xir}`;
+    return viewFileUsingTextDocumentContentProvider(ctx, requestType, uri, scheme, true);
+}
+
+function viewFileUsingTextDocumentContentProvider(
+    ctx: CtxInit,
+    requestType: lc.RequestType<lc.TextDocumentPositionParams, string, void>,
+    uri: string,
+    scheme: string,
+    shouldUpdate: boolean
+): Cmd {
     const tdcp = new (class implements vscode.TextDocumentContentProvider {
-        readonly uri = vscode.Uri.parse(`rust-analyzer-${xir}://${viewXir}/${xir}.rs`);
+        readonly uri = vscode.Uri.parse(uri);
         readonly eventEmitter = new vscode.EventEmitter<vscode.Uri>();
         constructor() {
             vscode.workspace.onDidChangeTextDocument(
@@ -439,14 +451,14 @@ function viewHirOrMir(ctx: CtxInit, xir: "hir" | "mir"): Cmd {
         }
 
         private onDidChangeTextDocument(event: vscode.TextDocumentChangeEvent) {
-            if (isRustDocument(event.document)) {
+            if (isRustDocument(event.document) && shouldUpdate) {
                 // We need to order this after language server updates, but there's no API for that.
                 // Hence, good old sleep().
                 void sleep(10).then(() => this.eventEmitter.fire(this.uri));
             }
         }
         private onDidChangeActiveTextEditor(editor: vscode.TextEditor | undefined) {
-            if (editor && isRustEditor(editor)) {
+            if (editor && isRustEditor(editor) && shouldUpdate) {
                 this.eventEmitter.fire(this.uri);
             }
         }
@@ -473,9 +485,7 @@ function viewHirOrMir(ctx: CtxInit, xir: "hir" | "mir"): Cmd {
         }
     })();
 
-    ctx.pushExtCleanup(
-        vscode.workspace.registerTextDocumentContentProvider(`rust-analyzer-${xir}`, tdcp)
-    );
+    ctx.pushExtCleanup(vscode.workspace.registerTextDocumentContentProvider(scheme, tdcp));
 
     return async () => {
         const document = await vscode.workspace.openTextDocument(tdcp.uri);
@@ -501,6 +511,20 @@ export function viewMir(ctx: CtxInit): Cmd {
     return viewHirOrMir(ctx, "mir");
 }
 
+// Opens the virtual file that will show the MIR of the function containing the cursor position
+//
+// The contents of the file come from the `TextDocumentContentProvider`
+export function interpretFunction(ctx: CtxInit): Cmd {
+    const uri = `rust-analyzer-interpret-function://interpretFunction/result.log`;
+    return viewFileUsingTextDocumentContentProvider(
+        ctx,
+        ra.interpretFunction,
+        uri,
+        `rust-analyzer-interpret-function`,
+        false
+    );
+}
+
 export function viewFileText(ctx: CtxInit): Cmd {
     const tdcp = new (class implements vscode.TextDocumentContentProvider {
         readonly uri = vscode.Uri.parse("rust-analyzer-file-text://viewFileText/file.rs");
diff --git a/editors/code/src/lsp_ext.ts b/editors/code/src/lsp_ext.ts
index 952dbb3e88a..754d43618a4 100644
--- a/editors/code/src/lsp_ext.ts
+++ b/editors/code/src/lsp_ext.ts
@@ -64,6 +64,9 @@ export const viewHir = new lc.RequestType<lc.TextDocumentPositionParams, string,
 export const viewMir = new lc.RequestType<lc.TextDocumentPositionParams, string, void>(
     "rust-analyzer/viewMir"
 );
+export const interpretFunction = new lc.RequestType<lc.TextDocumentPositionParams, string, void>(
+    "rust-analyzer/interpretFunction"
+);
 export const viewItemTree = new lc.RequestType<ViewItemTreeParams, string, void>(
     "rust-analyzer/viewItemTree"
 );
diff --git a/editors/code/src/main.ts b/editors/code/src/main.ts
index 6c990f804b0..7ae8fa8ca28 100644
--- a/editors/code/src/main.ts
+++ b/editors/code/src/main.ts
@@ -159,6 +159,7 @@ function createCommands(): Record<string, CommandFactory> {
         syntaxTree: { enabled: commands.syntaxTree },
         viewHir: { enabled: commands.viewHir },
         viewMir: { enabled: commands.viewMir },
+        interpretFunction: { enabled: commands.interpretFunction },
         viewFileText: { enabled: commands.viewFileText },
         viewItemTree: { enabled: commands.viewItemTree },
         viewCrateGraph: { enabled: commands.viewCrateGraph },